Method and apparatus for performing user equipment capability procedure for supporting vehicle communication in next generation mobile communication system

ABSTRACT

The disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method of performing user equipment capability procedure for supporting vehicle communication in a next generation mobile communication system is provided.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser. No. 16/789,686, filed on Feb. 13, 2020, which will be issued as U.S. Pat. No. 11,382,156 on Jul. 5, 2022, which is based on and claimed priority under 35 U.S.C. § 119(a) of a Korean patent application number 10-2019-0017418, filed on Feb. 14, 2019, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates to a method and apparatus for performing a user equipment capability procedure for supporting vehicle communication in a next generation mobile communication system. More particularly, the disclosure relates to a method and apparatus for configuring a measurement time period in a next generation mobile communication system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased since deployment of 4^(th) generation (4G) communication systems, efforts have been made to develop an improved 5^(th) generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post long term evolution (LTE) System’. The 5G communication system is considered to be implemented in higher frequency (mm Wave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems. In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like. In the 5G system, Hybrid frequency-shift keying (FSK) and quadrature amplitude modulation (QAM) (FOAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.

The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of Things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing Information Technology (IT) and various industrial applications.

In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, Machine Type Communication (MTC), and Machine-to-Machine (M2M) communication may be implemented by beamforming, MIMO, and array antennas. Application of a cloud Radio Access Network (RAN) as the above-described Big Data processing technology may also be considered to be as an example of convergence between the 5G technology and the IoT technology.

Recently, there is a need for a method of performing user equipment capability procedure for supporting vehicle communication in a next generation mobile communication system with development of Long Term Evolution (LTE) and LTE-Advanced.

The above information is presented as background information only to assist with an understanding of the disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the disclosure.

SUMMARY

Aspects of the disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide a method of performing user equipment capability procedure for supporting vehicle communication in a next generation mobile communication system.

Another aspect of the disclosure is to provide a method of configuration a measurement time period in a next generation mobile communication system.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments.

In accordance with an aspect of the disclosure, an efficient communication method between a user equipment (UE) and a base station that perform a UE capability procedure for supporting vehicle communication in a next generation mobile communication system are provided.

In accordance with another aspect of the disclosure, an efficient communication method between a UE and a base station that configure a measurement time period in a next generation mobile communication system are provided.

Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1A is a diagram illustrating a structure of an LTE system according to an embodiment of the disclosure;

FIG. 1B is a diagram illustrating a radio protocol architecture of an LTE system according to an embodiment of the disclosure;

FIG. 1C is a diagram illustrating a structure of a next generation mobile communication system according to an embodiment of the disclosure;

FIG. 1D is a diagram illustrating a radio protocol architecture of a next generation mobile communication system according to an embodiment of the disclosure;

FIG. 1E is a diagram vehicle-to-everything (V2X) communication by a next generation mobile communication system according to an embodiment of the disclosure;

FIG. 1F is a diagram illustrating a unicast link establishment procedure to support a new radio (NR) V2X sidelink (SL) unicast according to an embodiment of the disclosure;

FIG. 1G is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure;

FIG. 1H is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure;

FIG. 1I is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure;

FIG. 1J is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure;

FIG. 1K is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure;

FIG. 1L is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure;

FIG. 1M is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure;

FIG. 1N is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure;

FIG. 1O is a diagram illustrating a structure of a user equipment according to an embodiment of the disclosure;

FIG. 1P is a diagram illustrating a structure of a base station according to an embodiment of the disclosure;

FIG. 2A is a diagram illustrating a structure of a next generation mobile communication system according to an embodiment of the disclosure;

FIG. 2B is a diagram illustrating a dual-connection scenario in a next generation mobile communication system according to an embodiment of the disclosure;

FIGS. 2CA and 2CB are flowcharts illustrating a user equipment process of applying cell measurement period configuration in a dual-connection scenario in a 2-1 embodiment according to various embodiments of the disclosure;

FIG. 2D is a flowchart illustrating a user equipment process of applying cell measurement period configuration in a dual-connection scenario in a 2-2 embodiment according to an embodiment of the disclosure;

FIG. 2E is a block diagram illustrating an internal structure of a user equipment according to an embodiment of the disclosure; and

FIG. 2F is a block diagram illustrating a configuration of a base station according to an embodiment of the disclosure.

Throughout the drawings, like reference numerals will be understood to refer to like parts, components, and structures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the disclosure is provided for illustration purpose only and not for the purpose of limiting the disclosure as defined by the appended claims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces.

First Embodiment

FIG. 1A is a diagram illustrating a structure of an LTE system according to an embodiment of the disclosure.

Referring to FIG. 1A, a wireless access network of an LTE system may include: next generation base stations (Evolved Node B)(hereafter, ENB, Node B, or base station) 1 a-05, 1 a-10, 1 a-15, and 1 a-20; a Mobility Management Entity (MME) 1 a-25; and a Serving-Gateway (S-GW) 1 a-30. A user equipment (hereafter, UE or terminal) 1 a-35 may be connected to an external network through the ENBs 1 a-05 to 1 a-20 and the S-GW 1 a-30.

In FIG. 1A, the ENBs 1 a-05 to 1 a-20 may correspond to existing node Bs in a Universal Mobile Telecommunication System (UMTS). The ENBs may be connected to the UE 1 a-35 through a radio channel and can perform more complicated functions than the existing node Bs. In an LTE system, all user traffics including a real-time service such as a Voice over IP (VoIP) through an internet protocol may be serviced through a shared channel. Accordingly, there is a need for a device that performs scheduling by combining state information such as the buffer state, the available transmission power state, and the channel state of UEs, and the ENBs 1 a-05 to 1 a-20 can take charge of the device.

One ENB usually can control several cells. For example, in order to implement a transmission speed of 100 Mbps, an LTE system, for example, may use Orthogonal Frequency Division Multiplexing (OFDM) at a bandwidth of 20 MHz as a wireless connection technology. It may also possible to apply modulation scheme and Adaptive Modulation & Coding (AMC) determining a channel coding rate, depending on the channel state of a user equipment. The S-GW 1 a-30 is a device that provides a data bearer, and can generate or remove a data bearer in accordance with control by the MME 1 a-25. The MME, which is a device tacking charge of not only a mobility management function for UEs, but also various control functions, can be connected with several base stations.

FIG. 1B is a diagram illustrating a radio protocol architecture of an LTE system according to an embodiment of the disclosure.

Referring to FIG. 1B, the radio protocol of the LTE system may include Packet Data Convergence Protocols (PDCP) 1 b-05 and 1 b-40, Radio Link Controls (RLC) 1 b-10 and 1 b-35, and Medium Access Controls (MAC) 1 b-15 and 1 b-30 respectively in a user equipment and an ENB. The PDCP can take charge of operations such as IP header compression/restoration. The main functions of the PDCP may be summarized as follows.

-   -   Header compression and decompression (Header compression and         decompression: ROHC only)     -   Transmission of user data (Transfer of user data)     -   Sequential transmission (In-sequence delivery of upper layer         Protocol Data Units (PDUs) at PDCP re-establishment procedure         for RLC Acknowledged Mode (AM))     -   Reordering (For split bearers in Dual Connectivity (DC) (only         support for RLC AM): PDCP PDU routing for transmission and PDCP         PDU reordering for reception)     -   Duplicate detection (Duplicate detection of lower layer Service         Data Units (SDUs) at PDCP re-establishment procedure for RLC AM)     -   Retransmission (Retransmission of PDCP SDUs at handover and, for         split bearers in DC, of PDCP PDUs at PDCP data-recovery         procedure, for RLC AM)     -   Ciphering and deciphering     -   Timer-based SDU deletion (Timer-based SDU discard in uplink)     -   The RLCs 1 b-10 and 1 b-35 can perform an Automatic Repeat Query         (ARQ) operation, etc. by reconfiguring the PDCP PDU in an         appropriate size. The main functions of the RLC may be         summarized as follows.     -   Transmission of data (Transfer of upper layer PDUs)     -   ARQ function (Error Correction through ARQ (only for AM data         transfer))     -   Concatenation, segmentation and reassembly (Concatenation,         segmentation and reassembly of RLC SDUs (only for Unacknowledged         Mode (UM) and AM data transfer))     -   Re-segmentation (Re-segmentation of RLC data PDUs (only for AM         data transfer))     -   Reordering (Reordering of RLC data PDUs (only for UM and AM data         transfer)     -   Duplicate detection (Duplicate detection (only for UM and AM         data transfer))     -   Error detection (Protocol error detection (only for AM data         transfer))     -   RLC SDU deletion (RLC SDU discard (only for UM and AM data         transfer))     -   RLC re-establishment

The MACs 1 b-15 and 1 b-30 are connected with several RLC layer devices configured in one user equipment and can perform the operation of multiplexing RLC PDUs into an MAC PDU and demultiplexing RLC PDUs from an MAC PDU. The main functions of the MAC may be summarized as follows:

-   -   Mapping (Mapping between logical channels and transport         channels)     -   Multiplexing/demultiplexing (Multiplexing/demultiplexing of MAC         SDUs belonging to one or different logical channels into/from         transport blocks (TB) delivered to/from the physical layer on         transport channels)     -   Scheduling information reporting     -   Hybrid ARQ (HARQ) function (Error correction through HARQ)     -   Priority handling between logical channels (Priority handling         between logical channels of one UE)     -   Priority handling between UEs (Priority handling between UEs by         means of dynamic scheduling)     -   Multimedia Broadcast Multicast Services (MBMS) service         identification     -   Transport format selection     -   Padding

The physical layers 1 b-20 and 1 b-25 can perform make upper layer data into OFDM symbols by coding and modulating them and transmit the OFDM symbols to a radio channel or can demodulate OFDM symbols received through a radio channel, perform channel-decoding, and transmit them to an upper layer.

FIG. 1C is a diagram illustrating a structure of a next generation mobile communication system according to an embodiment of the disclosure.

Referring to FIG. 1C, a radio access network of a next generation mobile communication system (hereafter, NR or 5 g) may include a new radio node B (hereafter, NR gNB or NR base station) (1 c-10) and a New Radio Core Network (NR CN) 1 c-05. A New Radio User Equipment (NR UE or user equipment) 1 c-15 in a cell 1 c-20 can be connected to an external network through the NR gNB 1 c-10 and the NR CN 1 c-05.

In FIG. 1C, the NR gNB 1 c-10 may correspond to an Evolved Node B (eNB) of an existing LTE system. The NR gNB is connected with the NR UE 1 c-15 through a radio channel and can provide a superior service more than an existing node B. In a next generation mobile communication system, all user traffics can be serviced through a shared channel. Accordingly, there is a need for a device that performs scheduling by combining state information such as the buffer state, the available transmission power state, and the channel state of UEs, and the NR NB 1 c-10 can take charge of the device. One NR gNB usually can control several cells. In a next generation mobile communication system, a bandwidth over the current maximum bandwidth may be applied to implement high-speed data transmission in comparison to the current LTE. A beamforming technology may be employed by using Orthogonal Frequency Division Multiplexing (OFDM) as a radio connection technology. It may also possible to apply modulation scheme and Adaptive Modulation & Coding (hereafter, referred to as AMC) determining a channel coding rate, depending on the channel state of a user equipment.

The NR CN 1 c-05 can perform function such as mobility support, bearer configuration, and Quality of Service (QoS) configuration. The NR CN, which is a device being in charge of not only a mobility management function for UEs, but also various control functions, can be connected with several base stations. The next generation mobile communication systems may operate with an existing LTE system and the NR CN may be connected with the MME 1 c-25 through a network interface. The MME may be connected with the eNB 1 c-30 that is an existing base station.

FIG. 1D is a diagram illustrating a wireless protocol architecture of a next generation mobile communication system according to an embodiment of the disclosure.

Referring to FIG. 1D, a radio protocol of a next generation mobile communication system includes an NR Service Data Adaptation Protocols (SDAP) 1 d-01 and 1 d-45, NR PDCPs 1 d-05 and 1 d-40, NR RLC 1 d-10 and 1 d-35, NR MACs 1 d-15 and 1 d-30, and NR PHYs 1 d-20 and 1 d-25, respectively in a user equipment and an NR base station.

The main function of the NR SDAPs 1 d-01 and 1 d-45 may include some of the following functions:

-   -   Transmission of user data (Transfer of user plane data)     -   Mapping a QoS flow and a data bearer for an uplink and a         downlink (Mapping between a QoS flow and a Data Radio Bearer         (DRB) for both downlink (DL) and uplink (UL))     -   Marking a QoS flow Identifier (ID) for an uplink and a downlink         (Marking QoS flow ID in both DL and UL packets)     -   Mapping a reflective QoS flow to a data bearer for uplink SDAP         PDUs (reflective QoS flow to DRB mapping for the UL SDAP PDUs)

For an SDAP layer device, a user equipment can receive whether to use the header of the SDAP device or whether to use the function of the SDAP layer device for each of PDCP layer device, each bearer, or each logical channel through a Radio Resource Control (RRC) message. When an SDAP header is set, the user equipment can instruct a Non-Access Stratum (NAS) QoS (Quality of Service) reflective 1-bit indicator (NAS reflective QoS) and an Access Stratum (AS) QoS reflective 1-bit indicator (AS reflective QoS) of the SDAP header to update or reset the mapping information of the QoS flow and the data bearer of the uplink and the downlink. The SDAP header may include QoS flow ID information showing a QoS. The QoS information may be used as a data processing priority, scheduling information, etc. for supporting a smooth service.

The main function of the NR PDCP 1 d-05 and 1 d-40 may include some of the following functions:

-   -   Header compression and decompression (Header compression and         decompression: ROHC only)     -   Transmission of user data (Transfer of user data)     -   Sequence transmission (In-sequence delivery of upper layer PDUs)     -   Non-sequence transmission Out-of-sequence delivery of upper         layer PDUs)     -   Reordering (PDCP PDU reordering for reception)     -   Duplicate detection (Duplicate detection of lower layer SDUs)     -   Retransmission (Retransmission of PDCP SDUs)     -   Ciphering and deciphering     -   Timer-based SDU deletion (Timer-based SDU discard in uplink)

In the above description, the reordering of the NR DPCP device may mean a function of sequentially reordering PDCP PDU from a downlink, based on a PDCP SN (sequence number). The reordering of the NR PDCP device may include a function of transmitting data to an upper layer in a rearranged order, may include a function of directly transmitting data without considering the order, may include a function of recording missing PDCP PDUs by rearranging the order, may include a function of reporting the state of the missing PDCP PDUs to a transmission side, and may include a function of re-requesting retransmission of the missing PDCP PDUs.

The main function of the NR RLC 1 d-10 and 1 d-35) may include some of the following functions:

-   -   Transmission of data (Transfer of upper layer PDUs)     -   Sequence transmission (In-sequence delivery of upper layer PDUs)     -   Non-sequence transmission (Out-of-sequence delivery of upper         layer PDUs)     -   ARQ function (Error correction through ARQ)     -   Concatenation, segmentation and reassembly (Concatenation,         segmentation and reassembly of RLC SDUs)     -   Re-segmentation (Re-segmentation of RLC data PDUs)     -   Reordering (Reordering of RLC data PDUs)     -   Duplicate detection     -   Error detection (Protocol error detection)     -   RLC SDU deletion (RLC SDU discard)     -   RLC re-establishment

In the above description, the sequential transmission (in-sequence delivery) of the NR RLC device may mean a function of sequentially transmitting RLC SDUs received from a lower layer to an upper layer. When one RLC SDU is divided into several RLC SDUs and received, the sequential transmission (in-sequence delivery) of the NR RLC device may include a function of reassembling and transmitting the divided RLC SDUs.

The sequential transmission (in-sequence delivery) of the NR RLC device may include a function of reordering received RLC PDUs, based on RLC SNs (sequence number) or PDCP SNs (sequence number), may include a function of recording missing RLC PDUs by rearranging the order, may include a function of reporting the state of the missing RLC PDUs to a transmission side, and may include a function of re-requesting retransmission of the missing RLC PDUs.

The sequential transmission (in-sequence delivery) of the NR RLC devices 1 d-10 and 1 d-35 may include a function of transmitting only the RLC SDUs before the missing RLC SDUs to an upper layer when there are missing RLC SDUs. Further, the sequential transmission (in-sequence delivery) of the NR RLC device may include a function of sequentially transmitting all of RLC SDUs received before a predetermined timer starts to an upper layer if the predetermined timer is expired even if there is a missing RLC SDU. Further, the sequential transmission (in-sequence delivery) of the NR RLC device may include a function of sequentially transmitting all of RLC SDUs received up to now to an upper layer if the predetermined timer is expired even if there is a missing RLC SDU.

The NR RLC devices 1 d-10 and 1 d-35 can process and transmit RLC PDUs to the NR PDCP devices 1 d-05 and 1 d-40 in the reception order regardless of the order of the sequence numbers (out-of sequence delivery).

When the NR RLC devices 1 d-10 and 1 d-35 receive a segment, they can receive segments stored in a buffer or to be received later, reconfigure them into one complete RLC PDU, and then transmit it to the NR PDCP device.

The NR RLC layer may not include a concatenation function and can perform the function in an NR MAC layer or may replace the function with a multiplexing function of the NR MAC layer.

In the above description, the non-sequential transmission (out-of-sequence delivery) of the NR RLC device may mean a function of transmitting RLC SDUs received from a lower layer to the immediate upper layer regardless of the order. When non-sequential transmission (out-of-sequence delivery) of the NR RLC device may include a function of reassembling and transmitting divided RLC SDUs when one RLC SDU is divided into several RLC SDUs. The non-sequential transmission (out-of-sequence delivery) of the NR RLC device may include a function of storing the RLC SNs or the PDCP SNs of received RLC PDUs, reordering them, and recording missing RLC PDUs.

The NR MACs 1 d-15 and 1 d-30 may be connected with several NR RLC layer devices configured in one user equipment and the main function of the NR MACs may include some of the following functions:

-   -   Mapping (Mapping between logical channels and transport         channels)     -   Multiplexing/demultiplexing (Multiplexing/demultiplexing of MAC         SDUs)     -   Scheduling information reporting     -   HARQ function (Error correction through HARQ)     -   Priority handling between logical channels (Priority handling         between logical channels of one UE)     -   Priority handling between UEs (Priority handling between UEs by         means of dynamic scheduling)     -   MBMS service identification     -   Transport format selection     -   Padding

NR PHY layers 1 d-20 and 1 d-25 can make upper layer data into OFDM symbols by coding and modulating them and transmit the OFDM symbols to a radio channel or can demodulate OFDM symbols received through a radio channel, perform channel-decoding, and transmit them to an upper layer.

FIG. 1E is a diagram V2X communication by a next generation mobile communication system according to an embodiment of the disclosure.

V2X (vehicle-to-everything) according to an embodiment of the disclosure generally means a communication technology with a vehicle through all interfaces, and there are V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure), V2P (vehicle-to-pedestrian), V2N (vehicle-to-network), etc. in accordance with the type and the components for communication.

Referring to FIG. 1E, a base station 1 e-01 may include at least one vehicle UE 1 e-05 and 1 e-10 and pedestrian portable UE 1 e-15 that are included in a cell 1 e-02 supporting V2X. The V2X in this case can be supported through a Uu interface and/or a PC5 interface. The Uu interface is the radio interface between the mobile and the radio access network. When V2X is supported through a Uu interface, for example, the vehicle UEs 1 e-05 and 1 e-10 can perform V2X cellular communication using the base station 1 e-01 and a vehicle UE-base station uplink (UL)/downlink (DL) 1 e-30 and 1 e-35 and the pedestrian portable UE 1 e-15 can perform V2X cellular communication using a pedestrian UE-base station UL/DL 1 e-40. When V2X is supported by a PC5 interface, it is possible to perform V2X SL communication using UE-UE SLs 1 e-20 and 1 e-25. For example, the vehicle UE 1 e-05 existing in the coverage of the base station (in coverage of Evolved-Universal Terrestrial Radio Access (E-UTRA)/NR) can transmit/receive a V2X packet through SLs 1 e-20, 1 e-50, 1 e-25, and 1 e-60 that are transmission channels to/from other vehicle UEs 1 e-10 and 1 e-45 and/or pedestrian portable UEs 1 e-15 and 1 e-55. The V2X packet can be transmitted/received in a broadcast transmission type and/or a unicast and/or groupcast transmission type.

The UE that supports V2X SL communication can transmit/receive a V2X packet through a resource assignment mode (scheduled resource assignment or UE autonomous resource selection). Scheduled resource allocation (mode 1 and/or mode 3) is a mode in which a base station allocates resources that are used for slide link transmission in a dedicated scheduling type to an RRC connected mode equipment. The mode enables a base station to manage sidelink resources, it may be efficient in interference management and/or management of resource pool (dynamic allocation, semi-persistence transmission). When there are data to be transmitted to other equipment(s), the RRC connected mode UE can inform a base station that there are data to be transmitted to other UE(s) using an RRC message or an MAC control element (hereafter, CE). For example, the RRC message may be SidelinkUEInformation and UEAssistanceInformation messages, and the MAC CE may be a buffer state report MAC CE of a new format (including information about at least an indicator notifying a buffer report state for V2X communication and a data size buffered from sidelink communication).

UE autonomous resource selection (mode 2 and/or mode 4) is a mode in which a base station provides sidelink resource information/pool to a UE supporting side link communication through system information and/or an RRC message and the UE selects a resource in accordance with a predetermined rule. For example, a base station can provide sidelink resource information to equipment by signaling SIBx, etc. to be newly defined for an SIB21, SIB26, or NR V2X UE. As the RRC message, for example, a base station can provide sidelink resource information to a UE by signaling an RRC connected reconfiguration message (RRCReconfiguration message) and/or an RRC resume message (RRCResume message). UE autonomous resource selection may help a UE to select a resource to be used for a sidelink for other UE(s) through a PC5-RRC message and/or an MAC CE or may allocate a resource to be used for sidelink transmission through direct/indirect scheduling. That is, the UE autonomous resource selection mode may be referred to as one or a plurality of the following:

-   -   UE autonomously selects sidelink resource for transmission     -   UE assists sidelink resource selection for other UEs     -   UE is configured with NR configured grant for sidelink         transmission     -   UE schedules sidelink transmission of other UEs

A resource selection method of a UE may include zone mapping, sensing-based resource selection, random selection, and configured grant-based resource selection.

A UE that supports V2X SL communication can transmit/receive a V2X packet, based on a predetermined resource poll (Preconfiguration resource) included in SL-V2X-Preconfiguration that is an information element (hereafter, IE). For example, when a UE cannot perform V2X SL communication, based on the scheduled resource allocation and/or UE autonomous resource selection mode due to a predetermined reason even if the UE exists in the coverage of a base station, the UE can perform V2X SL communication through an SL transmission/reception resource pool preconfigured in the SL-V2X-Preconfiguration that is an IE. A vehicle UE 1 e-45 that is out of the coverage of base station (out-of-coverage of E-UTRA/NR) can perform V2X SL communication with another vehicle UE 1 e-65 or pedestrian portable UE 1 e-55, based on the SL Preconfiguration resource through the SLs 1 e-70 and 1 e-75 that are transmission channels.

LTE V2X SL communication is designed mainly for a basic safety service. That is, a UE supporting LTE V2X SL communication is designed to provide a basic safety service to all surrounding UEs supporting LTE V2X SL communication through a broadcast transmission type. Accordingly, the UE does not need to perform a process of separately making session with another specific UE or to perform a sidelink connection establishment procedure.

However, V2X SL communication may be designed to provide not only a basic safety service, but also various and improved services (for example, an autonomous service, a platooning service, a remote driving service, and an in-vehicle infotainment service) in next generation mobile communication (NR). Accordingly, NR V2X SL communication may be designed to be supported by not only a broadcast transmission type, but also a unicast and/or groupcast transmission type.

FIG. 1F is a diagram illustrating a unicast link establishment procedure to support an NR V2X SL unicast according to an embodiment of the disclosure.

Referring to FIG. 1F, in order to establish a UE-UE unicast link, a vehicle UE 1 f-01 can perform a discovery procedure (operation 1 f-03) with another vehicle UE 1 f-02. Accordingly, the vehicle UE 1 f-01 can acquire a link layer identifier of the vehicle UE 1 f-02. For example, the link layer identifier may mean a Layer 2 ID, a Destination Layer 2 ID, or a Destination ID that is used in NR V2X SL unicast communication.

When the operation 1 f-03 is finished, the vehicle UE 1 f-01 can perform an upper layer connection establishment procedure and/or an AS layer connection establishment procedure to establish UE-UE SL connection with the vehicle UE 1 f-02. Although the upper layer connection establishment procedure is described and then the AS layer connection establishment procedure is described for the convenience of description herein, the upper layer connection establishment procedure is described and the AS layer connection establishment procedure may be independently performed, or may be performed in parallel, or may be performed through one process.

The upper layer connection establishment procedure may be performed through next series of processes (operation 1 f-10, operation 1 f-20, operation 1 f-30, and operation 1 f-40) between UEs, based on a PC5 signaling protocol procedure defined in Rel-15 D2D.

-   -   The vehicle UE 1 f-01 transmits a DIRECT_COMMUNICATION_REQUEST         message to another vehicle UE 1 f-02 (operation 1 f-10):     -   It is the first PC5 signaling message that the vehicle UE 1 f-01         transmits to the vehicle UE 1 f-02 to request direct link         establishment (which is referred to a PC5 signaling message         because it is generated in a PC5 signaling protocol).     -   The vehicle UE 1 f-01 receives a DIRECT_SECURITY_MODE_COMMAND         message from the vehicle UE 1 f-02 (operation 1 f-20):     -   It is the first PC5 signaling message that the vehicle UE 1 f-02         transmits to the vehicle UE 1 f-01 to establish a direct         security mode while establishing the direct link (which is         referred to a PC5 signaling message because it is generated in a         PC5 signaling protocol).     -   The vehicle UE 1 f-01 transmits a DIRECT_SECURITY_MODE_COMPLETE         message to another vehicle UE 1 f-02 (operation 1 f-30):     -   It is a PC5 signaling message that the vehicle UE 1 f-01         transmits to inform the vehicle UE 1 f-02 that the direct         security mode has been successfully established/finished while         the direct link is established (which is referred to a PC5         signaling message because it is generated in a PC5 signaling         protocol).     -   The vehicle UE 1 f-01 transmits a DIRECT_COMMUNICATION_ACCEPT         message to another vehicle UE 1 f-02 (operation 1 f-40):     -   It is a PC5 signaling message that the vehicle UE 1 f-01         transmits to the vehicle UE 1 f-02 to inform the vehicle UE 1         f-02 that the direct link has been successfully established         (which is referred to a PC5 signaling message because it is         generated in a PC5 signaling protocol).

The PC5 signaling message that is transmitted/received during the upper layer connection process may include or not only some AS layer parameters and some of configuration information for establishing V2X SL connection between UEs. Accordingly, in order to establish V2X SL connection between UEs, not only the upper layer connection process, but also the AS layer connection procedure may be required.

The AS layer connection establishment procedure according to an embodiment of the disclosure may mean that the vehicle UE 1 f-01 and the vehicle UE 1 f-02 exchange AS layer parameters and configuration information for establishing V2X SL connection or NR V2X SL unicast communication through a PC5 RRC message. The PC5 RRC message may be transmitted/received through a logical channel that is generated in an RRC layer and newly defined in the NR. For example, the logical channel may be referred to as a Sidelink Control Channel (SCCH).

The PC5 RRC message (operation 1 f-a and/or 1 f-b and/or 1 f-c) according to an embodiment of the disclosure may include at least one of the next AS layer parameter and configuration information.

-   -   An indicator or an IE that asks or notify whether V2X SL unicast         communication support is available (or intension is available):     -   It is possible to check whether to perform V2X SL communication         between UEs using a unicast through the indicator or the IE. For         example, the vehicle UE 1 f-01 can ask whether a V2X SL unicast         is supported by transmitting a PC5-RRC message to another         vehicle UE 1 f-02, and as a response, the vehicle UE 1 f-02 can         inform the vehicle UE 1 f-01 that communication is possible         through the V2X SL unicast by transmitting a PC-5 RRC message.     -   UE ID: UE identifier:     -   It is possible to discriminate UEs that will perform or perform         V2X SL unicast communication through the UE ID. For example, the         UE ID may mean a Source Layer-2 ID and/or a Destination Layer-2         ID of a target UE for the unicast (herein, the target UE may         mean the vehicle UE 1 f-01 and/or the vehicle UE 1 f-02).         Alternatively, the UE ID may be a new Radio Network Temporary         Identifier (RNTI) that can discriminate UEs such as an RNTI, and         it is possible to perform an HARQ process between UEs, based on         the RNTI.     -   Radio bearer configuration: Radio bearer configuration         information:     -   It is possible to exchange an SRB ID for an SRB and/or a DRB ID         for a DRB that are used for NR V2X SL unicast communication         between vehicle UEs, and/or configuration information related to         a PDCP layer, and/or configuration information related to an         SDAP layer. For example, the radio bearer configuration         information may include some or all of srb-ToAddModList,         drb-ToAddModList, drb-ToReleaseList, securityConfig, etc. that         are information elements (hereafter, IE).     -   RLC bearer configuration: RLC bearer configuration information:     -   It is possible to exchange an ID for an SRB and/or a DRB used         for NR V2X SL unicast communication between vehicle UEs, a         logical channel ID (LCH-ID), an indicator showing whether it is         required to reestablish an RLC layer, configuration information         related to an RLC layer, and configuration information of an         MAC-logical channel through the RLC bearer configuration         information.     -   Configuration information for performing HARQ process:     -   It is possible to perform retransmission through an HARQ process         in NR V2X SL unicast communication between vehicle UEs. For         example, a timer for retransmission and a retransmission period         may be included.     -   QoS-related configuration information: 5QI (5G QoS Indicator)         VQI (V2X QoS Indicator) list/group:     -   It is possible to show QoS information for a desired V2X service         in NR V2X SL unicast communication between vehicle UEs through         the QoS-related configuration information. For example, a list         of 5QIs or VQIs may be included in the QoS-related configuration         information.     -   QoS-related configuration information: IE including a ProSe         Per-Packet Priority (PPPP) and/or Prose Per-Packet Reliability         (PPPR) list and/or traffic pattern information:     -   It is possible to show QoS information for a desired V2X service         or show information that performs Packet Duplication or perform         SPS or ConfiguredGrant Type 1 or ConfiguredGrant Type 2 in NR         V2X SL unicast communication between vehicle UEs through the         QoS-related configuration information. For example, the IE may         include PPPPInfoSL and/or reliabilityInfoListSL and/or         SL-V2X-PacketDuplicationConfig and/or trafficPatternInfoListSL.     -   IE including a ProSe Per-Packet Priority (PPPP) and/or Prose         Per-Packet Reliability (PPPR) list and/or traffic pattern         information:     -   It is possible to show QoS information for a desired V2X service         or show information that performs Packet Duplication or perform         SPS or ConfiguredGrant Type 1 or ConfiguredGrant Type 2 in NR         V2X SL unicast communication between vehicle UEs through the IE.         For example, the IE may include PPPPInfoSL and/or         reliabilityInfoListSL and/or SL-V2X-PacketDuplicationConfig         and/or trafficPatternInfoListSL.     -   IE including a ProSe Per-Packet Priority (PPPP) and/or Prose         Per-Packet Reliability (PPPR) list and/or traffic pattern         information:     -   It is possible to show QoS information for a desired V2X service         or show information that performs Packet Duplication or perform         SPS or ConfiguredGrant Type 1 or ConfiguredGrant Type 2 in NR         V2X SL unicast communication between vehicle UEs through the IE.         For example, the IE may include PPPPInfoSL and/or         reliabilityInfoListSL and/or SL-V2X-PacketDuplicationConfig         and/or trafficPatternInfoListSL.     -   Indicator or IE explicitly notifying whether to use a         Preconfiguration transmission resource pool and/or reception         resource pool:     -   It is possible to know whether to use a Preconfiguration         transmission resource pool and/or reception resource pool and         use a resource allocation mode-based transmission resource pool         and/or reception resource pool in NR V2X SL unicast         communication between vehicle UEs through the indicator or IE.     -   IE including an instructor explicitly notifying a resource         allocation mode, or some of a resource allocation mode-based         transmission resource pool and/or reception resource pool or a         Preconfiguration transmission resource pool and/or reception         resource pool:     -   It is possible to know whether to use some resources of a         Preconfiguration resource pool and/or reception resource pool         and use a resource allocation mode-based transmission resource         pool and/or reception resource pool in NR V2X SL unicast         communication between vehicle UEs through the indicator or IE.

The AS layer connection establishment procedure according to an embodiment of the disclosure may be performed independently from or in parallel with the upper layer connection establishment procedure or may be performed through one process. Accordingly, a point in time at which a PC5-RRC message (operation 1 f-a, operation 1 f-b, and operation 1 f-c) is proposed in the disclosure.

A first PC5-RRC message that the vehicle UE 1 f-01 transmits to another vehicle 1 f-02 to perform the an AS layer connection establishment procedure

-   -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 f-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 f-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 f-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 f-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 f-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 f-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 f-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 f-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 f-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 f-40) is received.

If the vehicle UE 1 f-02 receives the PC5-RRC message (operation 1 f-a) from the vehicle UE 1 f-01, the vehicle UE 1 f-02 can transmit a PC5-RRC message (operation 1 f-b) to the vehicle UE 1 f-01 as a response. The PC5-RRC message (operation 1 f-b):

-   -   may be transmitted after a PC5-RRC message (operation 1 f-a) is         received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 f-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 f-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 f-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 f-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 f-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 f-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 f-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 f-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 f-40) is transmitted.

If the vehicle UE 1 f-01 receives the PC5-RRC message (operation 1 f-b) from the vehicle UE 1 f-02, the vehicle UE 1 f-01 can transmit or not a PC5-RRC message (operation 1 f-c) to the vehicle UE 1 f-02 as a response. For example, when the upper layer connection establishment procedure and the AS layer connection establishment procedure are performed through one process, the vehicle UE 1 f-01 can provide a response to the PC5-RRC message (operation 1 f-b) to the vehicle UE 1 f-02 using a PC5 signaling message, so the vehicle UE 1 f-01 may not transmit a PC5-RRC message (operation 1 f-c). If when the PC5-RRC message (operation 1 f-c) needs to be transmitted, the PC5-RRC message (operation 1 f-c):

-   -   may be transmitted after a PC5-RRC message (operation 1 f-b) is         received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 f-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 f-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 f-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 f-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 f-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 f-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 f-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 f-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 f-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 f-40) is received.

FIG. 1G is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure.

Referring to FIG. 1G, a vehicle UE 1 g-01 can perform a discovery procedure (operation 1 g-03) with another vehicle UE 1 g-02 for NR V2X SL unicast communication. The vehicle UE 1 g-01 can perform an upper layer connection establishment procedure (operation 1 g-10, operation 1 g-20, operation 1 g-30, and operation 1 g-40) to establish SL connection with the vehicle UE 1 g-02. The upper layer connection establishment procedure may be performed through the embodiment described above.

The vehicle UE 1 g-01 can start a V2X SL UE capability transfer procedure when V2X sidelink radio access capability information of the vehicle UE 1 g-02 is required. The upper layer connection establishment procedure and the V2X SL UE capability transfer procedure may be independently performed, or may be performed in parallel, or may be performed through one process.

1. The vehicle UE 1 g-01 can transmit a message the requests the V2X sidelink radio access capability of the vehicle UE 1 g-02 (operation 1 g-a). For example, the message may be referred to as V2X-SL-UECapabilityEnquiry. The message may be transmitted through an SCCH as a PC5-RRC control message. The vehicle UE 1 g-01 can request a UE radio access capability for an NR V2X SL or a UE radio access capability for an LTE V2X SL from the vehicle UE 1 g-02 through the message. The message may include at least one of the following information:

A. V2X-SL-UE-CapabilityRAT-RequestList that is used to request V2X SL UE capability for one or more Radio Access Technologies (RAT) of the vehicle UE 1 g-02:

i. The V2X-SL-UE-CapabilityRAT-RequestList may include one or more V2X-SL-UE-CapabilityRAT-Request.

ii. Each V2X-SL-UE-CapabilityRequest may include rat-type indicating the type of a radio access technology. The rat-Type may indicate one of NR standalone, EUTRA standalone, and MR-DC. For example, the rat-Type may be indicated as one value of eutra-nr, eutra, and nr-eutra.

iii. Each V2X-SL-UE-CapabilityRequest may include information (v2x-SL-CapabilityRequestFilter) for filtering the V2X SL UE capability of the vehicle UE 1 g-02. For example, when the rat-Type is configured as nr (or eutra-nr), the v2x-SL-CapabilityRequestFilter may mean V2X-SL-UE-CapabilityRequestNR (or V2X-SL-UE-CapabilityMRDC).

2. The vehicle UE 1 g-02 receiving the message (e.g., V2X-SL-UECapabilityEnquiry) requesting V2X SL UE capability can compile its SL UE capability information to the vehicle UE 1 g-01 and can transmit a message including V2X SL UE capability information (operation 1 g-b). For example, the message may be referred to as V2X-SL-UECapabilityInformation. The message may be transmitted through an SCCH as a PC5-RRC control message.

A message that the vehicle UE 1 g-01 that has started the V2X SL UE capability transfer procedure transmits to the vehicle UE 1 g-02 to request V2X SL UE capability (operation 1 g-a):

-   -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 g-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 g-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 g-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 g-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 g-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 g-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 g-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 f-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 g-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 g-40) is received.

The message (operation 1 g-b) including V2X SL UE capability information that the vehicle UE 1 g-02 receiving the message (e.g., V2X-SL-UECapabilityEnquiry) requesting V2X SL UE capability transmits to the vehicle UE 1 g-01:

-   -   may be transmitted after a message (operation 1 g-a) requesting         V2X SL UE capability is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 g-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 g-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 g-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 g-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 g-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 g-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 g-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 g-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 f-40) is transmitted.

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 g-01 can perform a NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 g-02.

The vehicle UE 1 g-01 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 g-02 (operation 1 g-c). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a message (operation 1 g-b) including         V2X SL UE information is received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 g-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 g-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 g-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 g-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 g-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 g-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 g-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 g-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 g-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 g-40) is received.

The vehicle UE 1 g-02 can receive the PC5 RRC message (operation 1 g-c) transmitted from the vehicle UE 1 g-01, and when the message is applied, the vehicle UE 1 g-02 can transmit a PC5 RRC message to inform the vehicle UE 1 g-01 that the message has been confirmed (1 g-d). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above.

-   -   The message may be transmitted after a PC5 RRC message         (operation 1 g-c) including an AS layer parameter and         configuration information that can be applied to NR V2X SL         unicast communication is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 g-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 g-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 g-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 g-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 g-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 g-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 g-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 g-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 g-40) is transmitted.

The V2X SL UE capability transfer procedure according to an embodiment of the disclosure may be referred to as a 2-operation procedure. The 2-operation may have the following advantages:

-   -   When the vehicle UE 1 g-01 transmits a message for requesting UE         capability to the vehicle UE 1 g-02, information for filtering         the V2X SL UE capability of the vehicle UE 1 g-02 may be         included, so the vehicle UE 1 g-02 can transmit a message         including V2X SL UE capability information, based on filtered         information to the vehicle UE 1 g-01. That is, less information         may be included in the message including the V2X SL UE         capability information, so signaling overhead can be reduced.

However, the 2-operation may have the following disadvantages:

-   -   The vehicle UE 1 g-02 may not know at least some of the V2X SL         radio access capability information of the vehicle UE 1 g-01.         For example, when requiring V2X SL UE capability information of         the vehicle UE 1 g-01, the vehicle UE 1 g-02 may have to start         the 2-operation procedure or a NR V2X SL PC5 RRC connection         reconfiguration procedure. For example, it may be required to         perform operation 1 g-e, or operation 1 g-f, or operation 1 g-g,         or operation 1 g-h.

FIG. 1H is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure.

Referring to FIG. 1H, a vehicle UE 1 h-01 can perform a discovery procedure (operation 1 h-03) with another vehicle UE 1 h-02 for NR V2X SL unicast communication. The vehicle UE 1 h-01 can perform an upper layer connection establishment procedure (operation 1 h-10, operation 1 h-20, operation 1 h-30, and operation 1 h-40) to establish SL connection with the vehicle UE 1 h-02. The upper layer connection establishment procedure may be performed through the embodiment described above.

The vehicle UE 1 h-02 can start a V2X SL UE capability transfer procedure when V2X sidelink radio access capability information of the vehicle UE 1 h-01 is required. The upper layer connection establishment procedure and the V2X SL UE capability transfer procedure may be independently performed, or may be performed in parallel, or may be performed through one process.

1. The vehicle UE 1 h-02 can transmit a message that requests the V2X sidelink radio access capability information of the vehicle UE 1 h-01 (operation 1 h-a). For example, the message may be referred to as V2X-SL-UECapabilityEnquiry. The message may be transmitted through an SCCH as a PC5-RRC control message. The vehicle UE 1 h-02 can request a UE radio access capability for an NR V2X SL or a UE radio access capability for an LTE V2X SL from the vehicle UE 1 h-01 through the message. The message may include at least one of the following information:

A. V2X-SL-UE-CapabilityRAT-RequestList that is used to request V2X SL UE capability for one or more Radio Access Technologies (RAT) of the vehicle UE 1 h-01:

i. The V2X-SL-UE-CapabilityRAT-RequestList may include one or more V2X-SL-UE-CapabilityRAT-Request.

ii. Each V2X-SL-UE-CapabilityRequest may include rat-type indicating the type of a radio access technology. The rat-Type may indicate one of NR standalone, EUTRA standalone, and MR-DC. For example, the rat-Type may be indicated as one value of eutra-nr, eutra, and nr-eutra.

iii. Each V2X-SL-UE-CapabilityRequest may include information (v2x-SL-CapabilityRequestFilter) for filtering the V2X SL UE capability of the vehicle UE 1 h-01. For example, when the rat-Type is configured as nr (or eutra-nr), the v2x-SL-CapabilityRequestFilter may mean V2X-SL-UE-CapabilityRequestNR (or V2X-SL-UE-CapabilityMRDC).

2. The vehicle UE 1 h-01 receiving the message (e.g., V2X-SL-UECapabilityEnquiry) requesting V2X SL UE capability can compile its SL UE capability information to the vehicle UE 1 h-02 and can transmit a message including V2X SL UE capability information (operation 1 h-b). For example, the message may be referred to as V2X-SL-UECapabilityInformation. The message may be transmitted through an SCCH as a PC5-RRC control message.

A message that the vehicle UE 1 h-02 that has started the V2X SL UE capability transfer procedure transmits to the vehicle UE 1 h-01 to request V2X SL UE capability (operation 1 h-a):

-   -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 h-10) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 h-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 h-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 h-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 h-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 h-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 h-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 h-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 h-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (1 h-40) is transmitted.

The message (operation 1 h-b) including V2X SL UE capability information that the vehicle UE 1 h-01 receiving the message (e.g., V2X-SL-UECapabilityEnquiry) requesting V2X SL UE capability transmits to the vehicle UE 1 h-02:

-   -   may be transmitted after a message (operation 1 h-a) requesting         V2X SL UE capability is received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 h-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 h-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 h-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 h-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 h-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 h-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 h-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 h-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 h-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 h-40) is received.

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 h-02 can perform a NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 h-01.

The vehicle UE 1 h-02 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 h-01 (operation 1 h-c). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a message (operation 1 h-b) including         V2X SL UE information is received or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 h-10) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 h-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1H-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 h-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 h-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 h-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 h-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 h-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 h-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (1 h-40) is transmitted.

The vehicle UE 1 h-01 can receive the PC5 RRC message (operation 1 h-c) transmitted from the vehicle UE 1 h-02, and when the message is applied, the vehicle UE 1 h-01 can transmit a PC5 RRC message to inform the vehicle UE 1 h-02 that the message has been confirmed (1 h-d). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above.

-   -   The message may be transmitted after a PC5 RRC message         (operation 1 h-c) including an AS layer parameter and         configuration information that can be applied to NR V2X SL         unicast communication is received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 h-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 h-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 h-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 h-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 h-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 h-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 h-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 h-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 h-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 h-40) is received.

The V2X SL UE capability transfer procedure according to an embodiment of the disclosure may be referred to as a 2-operation procedure. The 2-operation may have the following advantages:

-   -   When the vehicle UE 1 h-02 transmits a message for requesting UE         capability to the vehicle UE 1 h-01, information for filtering         the V2X SL UE capability of the vehicle UE 1 h-01 may be         included, so the vehicle UE 1 h-01 can transmit a message         including V2X SL UE capability information, based on filtered         information to the vehicle UE 1 h-02. That is, less information         may be included in the message including the V2X SL UE         capability information, so signaling overhead can be reduced.

However, the 2-operation may have the following disadvantages:

-   -   The vehicle UE 1 h-01 may not know at least some of the V2X SL         UE capability information of the vehicle UE 1 h-02. For example,         when requiring V2X SL radio access capability information of the         vehicle UE 1 h-02, the vehicle UE 1 h-01 may have to start the         2-operation procedure or a NR V2X SL PC5 RRC connection         reconfiguration procedure. For example, it may be required to         perform operation 1 h-e, or operation 1 h-f, or operation 1 h-g,         or operation 1 h-h.

FIG. 1I is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure.

Referring to FIG. 1I, a vehicle UE 1 i-01 can perform a discovery procedure (operation 1 i-03) with another vehicle UE 1 i-02 for NR V2X SL unicast communication. The vehicle UE 1 i-01 can perform an upper layer connection establishment procedure (operation 1 i-10, operation 1 i-20, operation 1 i-30, and operation 1 i-40) to establish SL connection with the vehicle UE 1 i-02. The upper layer connection establishment procedure may be performed through the embodiment described above.

The vehicle UE 1 i-01 can start a V2X SL UE capability transfer procedure when transmitting V2X sidelink radio access capability information to the vehicle UE 1 i-02. The upper layer connection establishment procedure and the V2X SL UE capability transfer procedure may be independently performed, or may be performed in parallel, or may be performed through one process.

1. The vehicle UE 1 i-01 can transmit a message including the entire V2X SL UE capability information that it supports, to the vehicle UE 1 i-02 (operation 1 i-a). For example, the message may be referred to as V2X-SL-UECapabilityInformation. The message may be transmitted, including an indicator or an information element that shows the vehicle UE 1 i-02 does not need to transmit a message including V2X SL UE capability information. Alternatively, the message may include a Provider Service Identifier (PSID) of a V2X application, or Intelligent Transport System-Application Identifiers (ITS-AIDs), or a QoS rule mapped to an identifier such as new identifiers, or a 5G QoS Indicator (5QI) or a QoS Indicator (VQI), or a QoS Flow Indicator (QFI) based on a QoS parameter. Based on the information, the vehicle UE 1 i-02 can determine that it may not be required to send a message including V2X SL UE capability information to the vehicle UE 1 i-01.

The message may be transmitted through an SCCH as a PC5-RRC control message.

A message including V2X SL UE capability information that the vehicle UE 1 i-01 that has started the V2X SL UE capability transfer procedure transmits to the vehicle UE 1 i-02 (operation 1 i-a):

-   -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 i-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 i-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 i-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 i-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 i-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 i-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 i-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 i-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 i-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 i-40) is received.

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 i-02 can perform a NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 i-01.

The vehicle UE 1 i-02 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 i-01 (operation 1 i-b). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a message (operation 1 i-a) including         V2X SL UE information is received or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 i-10) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 i-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 i-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 i-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 i-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 i-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 i-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 i-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 i-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 i-40) is transmitted.

The vehicle UE 1 i-01 can receive the PC5 RRC message (operation 1 i-b) transmitted from the vehicle UE 1 i-02, and when the message is applied, the vehicle UE 1 i-01 can transmit a PC5 RRC message to inform the vehicle UE 1 i-02 that the message has been confirmed (1 i-c). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above.

-   -   The message may be transmitted after a PC5 RRC message         (operation 1 i-b) including an AS layer parameter and         configuration information that can be applied to NR V2X SL         unicast communication is received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 i-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 i-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 i-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 i-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 i-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 i-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 i-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 i-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 i-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 i-40) is received.

The V2X SL UE capability transfer procedure according to an embodiment of the disclosure may be referred to as a 1-operation procedure. The 1-operation may have the following advantages:

-   -   The vehicle UE 1 i-01 can transmit a message including V2X SL UE         capability information through one-time signaling to the vehicle         UE 1 i-02. That is, the signaling flow can be reduced in         comparison to the 2-operation, so latency can be decreased.

However, the 1-operation may have the following disadvantages:

-   -   When the vehicle UE 1 i-01 transmits a message including V2X SL         UE capability information to the vehicle UE 1 i-02, the message         may include much information in comparison to the 2-operation of         the embodiment described above. That is, this is because the         vehicle UE 1 i-01 has to transmit a message including the entire         supportable V2X SL UE capability information not filtered to the         vehicle UE 1 i-02.     -   The vehicle UE 1 i-01 may not know at least some of the V2X SL         UE capability information of the vehicle UE 1 i-02. For example,         when the vehicle UE 1 i-01 requires V2X SL radio access         capability information of the vehicle UE 1 i-02, the vehicle UE         1 i-01 may have to start the 1-operation procedure or the         vehicle UE 1 i-02 may have to start a NR V2X SL PC5 RRC         connection reconfiguration procedure. For example, it may be         required to perform operation 1 i-d, or operation 1 i-e, or         operation 1 i-f.

FIG. 1J is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure.

Referring to FIG. 1J, a vehicle UE 1 j-01 can perform a discovery procedure (operation 1 j-03) with another vehicle UE 1 j-02 for NR V2X SL unicast communication. The vehicle UE 1 j-01 can perform an upper layer connection establishment procedure (operation 1 j-10, operation 1 j-20, operation 1 j-30, and operation 1 j-40) to establish SL connection with the vehicle UE 1 j-02. The upper layer connection establishment procedure may be performed through the embodiment described above.

The vehicle UE 1 j-02 can start a V2X SL UE capability transfer procedure when transmitting V2X sidelink radio access capability information to the vehicle UE 1 j-02. The upper layer connection establishment procedure and the V2X SL UE capability transfer procedure may be independently performed, or may be performed in parallel, or may be performed through one process.

1. The vehicle UE 1 j-02 can transmit a message including the entire V2X SL UE capability information that it supports, to the vehicle UE 1 j-01 (operation 1 j-a). For example, the message may be referred to as V2X-SL-UECapabilityInformation. The message may be transmitted through an SCCH as a PC5-RRC control message.

A message including V2X SL UE capability information that the vehicle UE 1 j-02 that has started the V2X SL UE capability transfer procedure transmits to the vehicle UE 1 j-01 (operation 1 j-a):

-   -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 j-10) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 j-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 j-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 j-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 j-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 j-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 j-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 j-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 j-4) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 j-40) is transmitted.

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 j-01 can perform an NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 j-02.

The vehicle UE 1 j-01 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 j-02 (operation 1 j-b). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a message (operation 1 j-a) including         V2X SL UE information is received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 j-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 j-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 j-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 j-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 j-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 j-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 j-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 j-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 j-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 j-40) is received.

The vehicle UE 1 j-02 can receive the PC5 RRC message (operation 1 j-b) transmitted from the vehicle UE 1 j-01, and when the message is applied, the vehicle UE 1 j-02 can transmit a PC5 RRC message to inform the vehicle UE 1 j-01 that the message has been confirmed (1 j-c). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may be transmitted, including an indicator or an information element that shows the vehicle UE 1 j-01 does not need to transmit a message including V2X SL UE capability information. Alternatively, the message may include a Provider Service Identifier (PSID) of a V2X application, or Intelligent Transport System-Application Identifiers (ITS-AIDs), or a QoS rule mapped to an identifier such as new identifiers, or a 5G QoS Indicator (5QI) or a QoS Indicator (VQI), or a QoS Flow Indicator (QFI) based on a QoS parameter. Based on the information, the vehicle UE 1 j-01 can determine that it may not be required to send a message including V2X SL UE capability information to the vehicle UE 1 j-02. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above.

-   -   The message may be transmitted after a PC5 RRC message         (operation 1 j-b) including an AS layer parameter and         configuration information that can be applied to NR V2X SL         unicast communication is received or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 j-10) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 j-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 j-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 j-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 j-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 j-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 j-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 j-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 j-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 j-40) is transmitted.

The V2X SL UE capability transfer procedure according to an embodiment of the disclosure may be referred to as a 1-operation procedure. The 1-operation may have the following advantages:

-   -   The vehicle UE 1 j-02 can transmit a message including V2X SL UE         capability information through one-time signaling to the vehicle         UE 1 j-01. That is, the signaling flow can be reduced in         comparison to the 2-operation, so latency can be decreased.

However, the 1-operation may have the following disadvantages:

-   -   When the vehicle UE 1 j-02 transmits V2X SL UE capability         information to the vehicle UE 1 j-01, the message may include         much information in comparison to the 2-operation of the         embodiment described above. That is, this is because the vehicle         UE 1 j-02 has to transmit a message including the entire         supportable V2X SL UE capability information not filtered to the         vehicle UE 1 j-01.     -   The vehicle UE 1 j-02 may not know at least some of the V2X SL         UE capability information of the vehicle UE 1 j-01. For example,         when the vehicle UE 1 j-02 requires V2X SL radio access         capability information of the vehicle UE 1 j-01, the vehicle UE         1 j-01 may have to start the 1-operation procedure or the         vehicle UE 1 j-02 may have to start an NR V2X SL PC5 RRC         connection reconfiguration procedure. For example, it may be         required to perform operation 1 j-d, or operation 1 j-e, or         operation 1 j-f.

FIG. 1K is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure.

Referring to FIG. 1K, a vehicle UE 1 k-01 can perform a discovery procedure (operation 1 k-03) with another vehicle UE 1 k-02 for NR V2X SL unicast communication. The vehicle UE 1 k-01 can perform an upper layer connection establishment procedure (operation 1 k-10, operation 1 k-20, operation 1 k-30, and operation 1 k-40) to establish SL connection with the vehicle UE 1 k-02. The upper layer connection establishment procedure may be performed through the embodiment described above.

The vehicle UE 1 k-01 can start a V2X SL UE capability transfer procedure when V2X sidelink radio access capability information of the vehicle UE 1 k-02 is required. The upper layer connection establishment procedure and the V2X SL UE capability transfer procedure may be independently performed, or may be performed in parallel, or may be performed through one process.

1. The vehicle UE 1 k-01 can transmit a message the requests the V2X sidelink radio access capability information of the vehicle UE 1 k-02 (operation 1 k-a). For example, the message may be referred to as V2X-SL-UECapabilityEnquiry. The message may be transmitted through an SCCH as a PC5-RRC control message. The vehicle UE 1 k-01 can request a UE radio access capability for an NR V2X SL or a UE radio access capability for an LTE V2X SL from the vehicle UE 1 k-02 through the message. The message may include at least one of the following information:

B. V2X-SL-UE-CapabilityRAT-RequestList that is used to request V2X SL UE capability for one or more Radio Access Technologies (RAT) of the vehicle UE 1 k-02:

i. The V2X-SL-UE-CapabilityRAT-RequestList may include one or more V2X-SL-UE-CapabilityRAT-Request.

ii. Each V2X-SL-UE-CapabilityRequest may include rat-type indicating the type of a radio access technology. The rat-Type may indicate one of NR standalone, EUTRA standalone, and MR-DC. For example, the rat-Type may be indicated as one value of eutra-nr, eutra, and nr-eutra.

iii. Each V2X-SL-UE-CapabilityRequest may include information (v2x-SL-CapabilityRequestFilter) for filtering the V2X SL UE capability of the vehicle UE 1 k-02. For example, when the rat-Type is configured as an nr (or eutra-nr), v2x-SL-CapabilityRequestFilter may mean V2X-SL-UE-CapabilityRequestNR (or V2X-SL-UE-CapabilityMRDC).

C. An indicator or an information element indicating that the vehicle UE 1 k-01 transmits a message including V2X SL UE capability information of the vehicle UE 1 k-01 to the vehicle UE 1 k-02.

2. The vehicle UE 1 k-02 receiving the message (e.g., V2X-SL-UECapabilityEnquiry) requesting V2X SL UE capability can compile its SL UE capability information to the vehicle UE 1 k-01 and can transmit a message including V2X SL UE capability information (operation 1 k-b). For example, the message may be referred to as V2X-SL-UECapabilityInformation. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include an indicator or an information element requesting transmission of a message including V2X SL UE capability information that the vehicle UE 1 k-01 supports. Alternatively, the message may include a Provider Service Identifier (PSID) of a V2X application, or Intelligent Transport System-Application Identifiers (ITS-AIDs), or a QoS rule mapped to an identifier such as new identifiers, or a 5G QoS Indicator (5QI) or a V2X QoS Indicator (VQI), or a QoS Flow Indicator (QFI) based on a QoS parameter. Based on the information, the vehicle UE 1 k-01 can determine that it may not be required to send a message including V2X SL UE capability information to the vehicle UE 1 k-02.

3. The vehicle UE 1 k-01 can transmit a message including V2X SL UE capability information that the vehicle UE 1 k-01 supports, to the vehicle UE 1 k-02 (operation 1 k-c). For example, the message may be referred to as V2X-SL-UECapabilityInformationComplete. The message may be transmitted through an SCCH as a PC5-RRC control message. The message can be transmitted when an indicator or an information element that indicates that the vehicle UE 1 k-01 transmits a message including the V2X SL UE capability information of the vehicle UE 1 k-01 to the vehicle UE 1 k-02 in operation 1 k-a is included or when an indicator or an information element that requests transmission of a message including V2X SL UE capability information that the vehicle UE 1 k-01 supports in operation 1 k-b is included. Alternatively, the message may be transmitted anytime.

A message that the vehicle UE 1 k-01 that has started the V2X SL UE capability transfer procedure transmits to the vehicle UE 1 k-02 to request V2X SL UE capability (operation 1 k-a):

-   -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 k-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 k-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 k-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 k-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 k-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 k-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 k-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 k-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 k-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 k-40) is received.

The message (operation 1 k-b) including V2X SL UE capability information that the vehicle UE 1 k-02 receiving the message (e.g., V2X-SL-UECapabilityEnquiry) requesting V2X SL UE capability transmits to the vehicle UE 1 k-01:

-   -   may be transmitted after a message (operation 1 k-a) requesting         V2X SL UE capability is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 k-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 k-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 k-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 k-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 k-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 k-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 k-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 k-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 k-40) is transmitted.

The message (operation 1 k-c) including V2X SL UE capability information that the vehicle UE 1 k-01 receiving the message (e.g., V2X-SL-UECapabilityEnquiry) including V2X SL UE capability information transmits to the vehicle UE 1 k-02:

-   -   may be transmitted after a message (operation 1 k-b) including         V2X SL UE capability information is received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 k-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 k-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 k-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 k-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 k-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 k-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 k-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 k-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 k-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 k-40) is received.

When the vehicle UE 1 k-01 transmits the message (1 k-c) to the vehicle UE 1 k-02, the vehicle UE 1 k-01 can transmit the message 1 k-c to the vehicle UE 1 k-02, including only V2X SL UE capability information that the vehicle UE 1 k-01 can support, based on the message (1 k-b) including the received V2X SL UE capability information. That is, the message (operation 1 k-c) may include a portion of or the entire received message (operation 1 k-b). Alternatively, the message (operation 1 k-c) may indicate only V2X SL UE capability information that can be supported in the received message (operation 1 k-b). Alternatively, the message (operation 1 k-c) may indicate only V2X SL UE capability information that cannot be supported in the received message (operation 1 k-b).

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 k-01 can perform a NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 k-02.

The vehicle UE 1 k-01 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 k-02 (operation 1 k-b). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a message (operation 1 k-b) including         V2X SL UE information is received or     -   may be transmitted simultaneously with a message (operation 1         k-c) including V2X SL UE information or     -   may be multiplexed and transmitted with a message (operation 1         k-c) including V2X SL UE information is received or     -   may be transmitted after a message (operation 1 k-c) including         V2X SL UE information is transmitted or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 k-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 k-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 k-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 k-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 k-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 k-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 k-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 k-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 k-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 k-40) is received.

The vehicle UE 1 k-02 can receive the PC5 RRC message (operation 1 k-c) transmitted from the vehicle UE 1 k-01, and when the message is applied, the vehicle UE 1 k-02 can transmit a PC5 RRC message to inform the vehicle UE 1 k-01 that the message has been confirmed (1 k-c). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above.

-   -   The message may be transmitted after a PC5 RRC message         (operation 1 k-d) including an AS layer parameter and         configuration information that can be applied to NR V2X SL         unicast communication is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 k-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 k-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 k-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 k-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 k-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 k-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 k-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 k-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 k-40) is transmitted.

The V2X SL UE capability transfer procedure according to an embodiment of the disclosure may be referred to as a 3-operation procedure. The 3-operation may have the following advantages:

-   -   When the vehicle UE 1 k-01 transmits a message for requesting UE         capability to the vehicle UE 1 k-02, information for filtering         the V2X SL UE capability of the vehicle UE 1 k-02 may be         included, so the vehicle UE 1 k-02 can transmit a message         including V2X SL UE capability information, based on filtered         information to the vehicle UE 1 k-01. That is, less information         may be included in the message including the V2X SL UE         capability information, so signaling overhead can be reduced.     -   When the vehicle UE 1 k-02 does not know at least some of the         V2X SL UE capability information that the vehicle UE 1 k-01         supports, the vehicle UE 1 k-01 performs the last operation of         the 3-operation, whereby the vehicle UE 1 k-02 can know the V2X         SL UE capability information that the vehicle UE 1 k-01         supports.     -   The vehicle UE 1 k-01 performs the last operation, including         only V2X SL UE capability information that the vehicle UE 1 k-01         can support of the V2X SL UE capability information that the         vehicle UE 1 k-02 can support, to the vehicle UE 1 k-02, thereby         being able to reduce signaling overhead.

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 k-02 can perform a NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 k-01.

The vehicle UE 1 k-01 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 k-01 (operation 1 k-f). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a message (operation 1 k-c) including         V2X SL UE information is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 k-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 k-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 k-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 k-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 k-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 k-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 k-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 k-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 k-40) is transmitted.

The vehicle UE 1 k-01 can receive the PC5 RRC message (operation 1 k-f) transmitted from the vehicle UE 1 k-02, and when the message is applied, the vehicle UE 1 k-02 can transmit a PC5 RRC message to inform the vehicle UE 1 k-01 that the message has been confirmed (1 k-g). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a PC5 RRC message (operation 1 k-f)         including an AS layer parameter and configuration information         that can be applied to NR V2X SL unicast communication is         received or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 k-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 k-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 k-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 k-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 k-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 k-40) is received.

The 3-operation may have the advantages described above.

FIG. 1L is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure.

Referring to FIG. 1L, a vehicle UE 1 l-01 can perform a discovery procedure (operation 1 l-03) with another vehicle UE 1 l-02 for NR V2X SL unicast communication. The vehicle UE 1 l-01 can perform an upper layer connection establishment procedure (operation 1 l-10, operation 1 l-20, operation 1 l-30, and operation 1 l-40) to establish SL connection with the vehicle UE 1 l-02. The upper layer connection establishment procedure may be performed through the embodiment described above.

The vehicle UE 1 l-02 can start a V2X SL UE capability transfer procedure when V2X sidelink radio access capability information of the vehicle UE 1 l-01 is required. The upper layer connection establishment procedure and the V2X SL UE capability transfer procedure may be independently performed, or may be performed in parallel, or may be performed through one process.

1. The vehicle UE 1 l-02 can transmit a message that requests the V2X sidelink radio access capability information of the vehicle UE 1 l-01 (operation 1 l-a). For example, the message may be referred to as V2X-SL-UECapabilityEnquiry. The message may be transmitted through an SCCH as a PC5-RRC control message. The vehicle UE 1 l-02 can request a UE radio access capability for an NR V2X SL or a UE radio access capability for an LTE V2X SL from the vehicle UE 1 l-01 through the message. The message may include at least one of the following information:

A. V2X-SL-UE-CapabilityRAT-RequestList that is used to request V2X SL UE capability for one or more Radio Access Technologies (RAT) of the vehicle UE 1 l-01:

i. The V2X-SL-UE-CapabilityRAT-RequestList may include one or more V2X-SL-UE-CapabilityRAT-Request.

ii. Each V2X-SL-UE-CapabilityRequest may include rat-type indicating the type of a radio access technology. The rat-Type may indicate one of NR standalone, EUTRA standalone, and MR-DC. For example, the rat-Type may be indicated as one value of eutra-nr, eutra, and nr-eutra.

iii. Each V2X-SL-UE-CapabilityRequest may include information (v2x-SL-CapabilityRequestFilter) for filtering the V2X SL UE capability of the vehicle UE 1 l-01. For example, when the rat-Type is configured as nr (or eutra-nr), the v2x-SL-CapabilityRequestFilter may mean V2X-SL-UE-CapabilityRequestNR (or V2X-SL-UE-CapabilityMRDC).

B. An indicator or an information element indicating that the vehicle UE 1 l-02 transmits a message including V2X SL UE capability information of the vehicle UE 1 l-02 to the vehicle UE 1 k-01.

2. The vehicle UE 1 l-01 receiving the message (e.g., V2X-SL-UECapabilityEnquiry) requesting V2X SL UE capability can compile its SL UE capability information to the vehicle UE 1 l-02 and can transmit a message including V2X SL UE capability information (operation 1 l-b). For example, the message may be referred to as V2X-SL-UECapabilityInformation. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include an indicator or an information element requesting transmission of a message including V2X SL UE capability information that the vehicle UE 1 l-02 supports. Alternatively, the message may include a Provider Service Identifier (PSID) of a V2X application, or Intelligent Transport System-Application Identifiers (ITS-AIDs), or a QoS rule mapped to an identifier such as new identifiers, or a 5G QoS Indicator (5QI) or a QoS Indicator (VQI), or a QoS Flow Indicator (QFI) based on a QoS parameter. Based on the information, the vehicle UE 1 l-02 can determine that it may not be required to send a message including V2X SL UE capability information to the vehicle UE 1 l-01.

3. The vehicle UE 1 l-02 can transmit a message including V2X SL UE capability information that the vehicle UE 1 l-02 supports, to the vehicle UE 1 l-01 (operation 1 l-c). For example, the message may be referred to as V2X-SL-UECapabilityInformationComplete. The message may be transmitted through an SCCH as a PC5-RRC control message. The message can be transmitted when an indicator or an information element that indicates that the vehicle UE 1 k-02 transmits a message including the V2X SL UE capability information of the vehicle UE 1 l-02 to the vehicle UE 1 k-01 in operation 1 l-a is included or when an indicator or an information element that requests transmission of a message including V2X SL UE capability information that the vehicle UE 1 l-01 supports in operation 1 l-b is included. Alternatively, the message may be transmitted anytime.

A message that the vehicle UE 1 l-02 that has started the V2X SL UE capability transfer procedure transmits to the vehicle UE 1 l-01 to request V2X SL UE capability (operation 1 l-a):

-   -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 l-10) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 l-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 l-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 l-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 l-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 l-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 l-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 l-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 l-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 l-40) is transmitted.

The message (operation 1 l-b) including V2X SL UE capability information that the vehicle UE 1 l-01 receiving the message (e.g., V2X-SL-UECapabilityEnquiry) requesting V2X SL UE capability transmits to the vehicle UE 1 l-02:

-   -   may be transmitted after a message (operation 1 l-a) requesting         V2X SL UE capability is received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 l-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 l-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 l-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 l-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 l-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 l-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 l-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 l-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 l-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 l-40) is received.

The message (operation 1 l-c) including V2X SL UE capability information that the vehicle UE 1 l-02 receiving the message (e.g., V2X-SL-UECapabilityEnquiry) including V2X SL UE capability information transmits to the vehicle UE 1 l-01:

-   -   may be transmitted after a message (operation 1 l-b) requesting         V2X SL UE capability is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 l-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 l-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 l-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 l-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 l-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 l-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 l-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 l-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 l-40) is transmitted.

When the vehicle UE 1 l-02 transmits the message (1 l-c) to the vehicle UE 1 l-01, the vehicle UE 1 l-02 can transmit the message (operation 1 l-c) to the vehicle UE 1 l-01, including only V2X SL UE capability information that the vehicle UE 1 l-02 can support, based on the message (operation 1 l-b) including the received V2X SL UE capability information. That is, the message (operation 1 l-c) may include a portion of or the entire received message (operation 1 l-b). Alternatively, the message (operation 1 l-c) may indicate only V2X SL UE capability information that can be supported in the received message (operation 1 l-b). Alternatively, the message (operation 1 l-c) may indicate only V2X SL UE capability information that cannot be supported in the received message (operation 1 l-b).

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 l-02 can perform a NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 l-01.

The vehicle UE 1 l-01 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 l-02 (operation 1 l-d). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a message (operation 1 l-c) including         V2X SL UE information is received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 l-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 l-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 l-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 l-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 l-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 l-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 l-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 l-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 l-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 l-40) is received.

The vehicle UE 1 l-02 can receive the PC5 RRC message (operation 1 l-c) transmitted from the vehicle UE 1 l-01, and when the message is applied, the vehicle UE 1 l-02 can transmit a PC5 RRC message to inform the vehicle UE 1 l-01 that the message has been confirmed (operation 1 l-e). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a PC5 RRC message (operation 1 l-d)         including an AS layer parameter and configuration information         that can be applied to NR V2X SL unicast communication is         received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 l-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 l-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 l-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 l-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 l-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 l-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 l-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 l-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 l-40) is transmitted.

The V2X SL UE capability transfer procedure according to an embodiment of the disclosure may be referred to as a 3-operation procedure. The 3-operation may have the following advantages:

-   -   When the vehicle UE 1 l-02 transmits a message for requesting UE         capability to the vehicle UE 1 l-01, information for filtering         the V2X SL UE capability of the vehicle UE 1 l-01 may be         included, so the vehicle UE 1 l-01 can transmit a message         including V2X SL UE capability information, based on filtered         information to the vehicle UE 1 l-02. That is, less information         may be included in the message including the V2X SL UE         capability information, so signaling overhead can be reduced.     -   When the vehicle UE 1 l-01 does not know at least some of the         V2X SL UE capability information that the vehicle UE 1 l-02         supports, the vehicle UE 1 l-02 performs the last operation of         the 3-operation, whereby the vehicle UE 1 l-01 can know the V2X         SL UE capability information that the vehicle UE 1 l-02         supports.     -   The vehicle UE 1 l-02 performs the last operation, including         only V2X SL UE capability information that the vehicle UE 1 l-02         can support of the V2X SL UE capability information that the         vehicle UE 1 k-01 can support, to the vehicle UE 1 l-01, thereby         being able to reduce signaling overhead.

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 l-02 can perform a NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 l-01.

The vehicle UE 1 l-01 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 l-01 (operation 1 l-f). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted simultaneously with a message (operation 1         l-c) including V2X SL UE information or     -   may be multiplexed and transmitted with a message (operation 1         l-c) including V2X SL UE information or     -   may be transmitted after a message (operation 1 l-c) including         V2X SL UE information is transmitted or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 l-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 l-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 l-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 l-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 l-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 l-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 l-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 l-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 l-40) is transmitted.

The vehicle UE 1 l-01 can receive the PC5 RRC message (operation 1 l-c) transmitted from the vehicle UE 1 l-02, and when the message is applied, the vehicle UE 1 l-01 can transmit a PC5 RRC message to inform the vehicle UE 1 l-02 that the message has been confirmed (operation 1 l-g). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a PC5 RRC message (operation 1 l-0         including an AS layer parameter and configuration information         that can be applied to NR V2X SL unicast communication is         received or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 l-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 l-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 l-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 l-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 l-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 l-40) is received.

The 3-operation may have the advantages described above.

FIG. 1M is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure.

Referring to FIG. 1M, a vehicle UE 1 m-01 can perform a discovery procedure (operation 1 m-03) with another vehicle UE 1 m-02 for NR V2X SL unicast communication. The vehicle UE 1 m-01 can perform an upper layer connection establishment procedure (operation 1 m-10, operation 1 m-20, operation 1 m-30, and operation 1 m-40) to establish SL connection with the vehicle UE 1 m-02. The upper layer connection establishment procedure may be performed through the embodiment described above.

The vehicle UE 1 m-01 can start a V2X SL UE capability transfer procedure when transmitting V2X sidelink radio access capability information to the vehicle UE 1 m-02. The upper layer connection establishment procedure and the V2X SL UE capability transfer procedure may be independently performed, or may be performed in parallel, or may be performed through one process.

1. The vehicle UE 1 m-01 can transmit a message including the entire V2X SL UE capability information that it supports, to the vehicle UE 1 m-02 (operation 1 m-a). For example, the message may be referred to as V2X-SL-UECapabilityInformation. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include an indicator or an information element requesting transmission of a message including V2X SL UE capability information that the vehicle UE 1 m-02 supports. Alternatively, the message may include a Provider Service Identifier (PSID) of a V2X application, or Intelligent Transport System-Application Identifiers (ITS-AIDs), or a QoS rule mapped to an identifier such as new identifiers, or a 5G QoS Indicator (5QI) or a QoS Indicator (VQI), or a QoS Flow Indicator (QFI) based on a QoS parameter. Based on the information, the vehicle UE 1 m-02 can determine that it may not be required to send a message including V2X SL UE capability information to the vehicle UE 1 m-01.

2. The vehicle UE 1 m-02 can transmit a message including V2X SL UE capability information that the vehicle UE 1 m-02 supports, to the vehicle UE 1 m-01 (operation 1 m-b). For example, the message may be referred to as V2X-SL-UECapabilityInformationComplete. The message may be transmitted through an SCCH as a PC5-RRC control message. The message can be transmitted when an indicator or an information element indicating that the vehicle UE 1 m-01 transmits a message including V2X SL UE capability information of the vehicle UE 1 m-02 to the vehicle UE 1 m-02 is included in operation 1 m-a. Alternatively, the message may be transmitted anytime.

A message including V2X SL UE capability (operation 1 m-a) that the vehicle UE 1 m-01 that has started the V2X SL UE capability transfer procedure transmits to the vehicle UE 1 m-02:

-   -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 m-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 m-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 m-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 m-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 m-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 m-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 m-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 m-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 m-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 m-40) is received.

The message (operation 1 m-b) including V2X SL UE capability information that the vehicle UE 1 m-02 receiving the message (e.g., V2X-SL-UECapabilityInformation) including V2X SL UE capability information transmits to the vehicle UE 1 m-01:

-   -   may be transmitted after a message (operation 1 m-a) including         V2X SL UE information is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 m-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 m-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 m-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 m-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 m-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 m-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 m-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 m-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 m-40) is transmitted.

When the vehicle UE 1 m-02 transmits the message (operation 1 m-b) to the vehicle UE 1 m-01, the vehicle UE 1 m-02 can transmit the message (operation 1 m-b) to the vehicle UE 1 m-01, including only V2X SL UE capability information that the vehicle UE 1 m-02 can support, based on the message (operation 1 m-a) including the received V2X SL UE capability information. That is, the message (operation 1 m-b) may include a portion of or the entire received message (operation 1 m-a). Alternatively, the message (operation 1 m-b) may indicate only V2X SL UE capability information that can be supported in the received message (operation 1 m-a). Alternatively, the message (operation 1 m-b) may indicate only V2X SL UE capability information that cannot be supported in the received message (operation 1 m-a).

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 m-01 can perform a NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 m-02.

The vehicle UE 1 m-01 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 m-02 (operation 1 m-c). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a message (operation 1 m-b) including         V2X SL UE information is received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 m-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 m-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 m-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 m-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 m-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 m-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 m-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 m-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 m-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 m-40) is received.

The vehicle UE 1 m-02 can receive the PC5 RRC message (operation 1 m-c) transmitted from the vehicle UE 1 m-01, and when the message is applied, the vehicle UE 1 m-02 can transmit a PC5 RRC message to inform the vehicle UE 1 m-01 that the message has been confirmed (operation 1 m-e). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a PC5 RRC message (operation 1 m-c)         including an AS layer parameter and configuration information         that can be applied to NR V2X SL unicast communication is         received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 m-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 m-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 m-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 m-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 m-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 m-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 m-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 m-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 m-40) is transmitted.

The V2X SL UE capability transfer procedure according to an embodiment of the disclosure may be referred to as a 2-operation procedure. The 2-operation may have the following advantages:

-   -   The vehicle UE 1 m-01 can transmit a message including V2X SL UE         capability information through one-time signaling to the vehicle         UE 1 m-02. That is, the signaling flow can be reduced, so         latency can be decreased.     -   When the vehicle UE 1 m-01 does not know at least some of the         V2X SL UE capability information of the vehicle UE 1 m-02, the         vehicle UE 1 m-02 performs the last operation of the         2-operation, whereby the vehicle UE 1 m-01 can know the V2X SL         UE capability information that the vehicle UE 1 m-02 supports.     -   The vehicle UE 1 m-02 performs the last operation, including         only V2X SL UE capability information that the vehicle UE 1 m-02         can support of the V2X SL UE capability information that the         vehicle UE 1 m-01 can support, to the vehicle UE 1 m-01, thereby         being able to reduce signaling overhead.

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 m-02 can perform a NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 m-01.

The vehicle UE 1 m-02 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 m-01 (operation 1 m-e). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted simultaneously with a message (operation 1         m-b) including V2X SL UE information or     -   may be multiplexed and transmitted with a message (operation 1         m-b) including V2X SL UE information or     -   may be transmitted after a message (operation 1 m-b) including         V2X SL UE information is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 m-10) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 m-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 m-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 m-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 m-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 m-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 m-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 m-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 m-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 m-40) is transmitted.

The vehicle UE 1 m-01 can receive the PC5 RRC message (operation 1 m-e) transmitted from the vehicle UE 1 m-02, and when the message is applied, the vehicle UE 1 m-01 can transmit a PC5 RRC message to inform the vehicle UE 1 m-02 that the message has been confirmed (operation 1 m-f). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above.

-   -   The message may be transmitted after a PC5 RRC message         (operation 1 m-e) including an AS layer parameter and         configuration information that can be applied to NR V2X SL         unicast communication is received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 m-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 m-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 m-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 m-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 m-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 m-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 m-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 m-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 m-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 m-40) is received.

The 2-operation may have the advantages described above.

FIG. 1N is a diagram illustrating a V2X SL UE capability transfer procedure to perform NR V2X SL unicast communication between user equipments according to an embodiment of the disclosure.

Referring to FIG. 1N, a vehicle UE 1 n-01 can perform a discovery procedure (operation 1 n-03) with another vehicle UE 1 n-02 for NR V2X SL unicast communication. The vehicle UE 1 n-01 can perform an upper layer connection establishment procedure (operation 1 n-10, operation 1 n-20, operation 1 n-30, and operation 1 n-40) to establish SL connection with the vehicle UE 1 n-02. The upper layer connection establishment procedure may be performed through the embodiment described above.

The vehicle UE 1 n-02 can start a V2X SL UE capability transfer procedure when transmitting V2X sidelink radio access capability information to the vehicle UE 1 n-01. The upper layer connection establishment procedure and the V2X SL UE capability transfer procedure may be independently performed, or may be performed in parallel, or may be performed through one process.

1. The vehicle UE 1 n-02 can transmit a message including the entire V2X SL UE capability information that it supports, to the vehicle UE 1 n-01 (operation 1 n-a). For example, the message may be referred to as V2X-SL-UECapabilityInformation. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include an indicator or an information element requesting transmission of a message including V2X SL UE capability information that the vehicle UE 1 n-01 supports. Alternatively, the message may include a Provider Service Identifier (PSID) of a V2X application, or Intelligent Transport System-Application Identifiers (ITS-AIDs), or a QoS rule mapped to an identifier such as new identifiers, or a 5G QoS Indicator (5QI) or V2X a QoS Indicator (VQI), or a QoS Flow Indicator (QFI) based on a QoS parameter. Based on the information, the vehicle UE 1 n-01 can determine that it may not be required to send a message including V2X SL UE capability information to the vehicle 1 n-02.

2. The vehicle UE 1 n-01 can transmit a message including V2X SL UE capability information that the vehicle UE 1 n-01 supports, to the vehicle UE 1 n-02 (operation 1 n-b). For example, the message may be referred to as V2X-SL-UECapabilityInformationComplete. The message may be transmitted through an SCCH as a PC5-RRC control message. The message can be transmitted when an indicator or an information element indicating that the vehicle UE 1 n-01 transmits a message including V2X SL UE capability information of the vehicle UE 1 n-01 to the vehicle UE 1 n-01 is included in operation 1 n-a. Alternatively, the message may be transmitted anytime.

A message including V2X SL UE capability information that the vehicle UE 1 n-02 that has started the V2X SL UE capability transfer procedure transmits to the vehicle UE 1 n-01 (operation 1 n-a):

-   -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 n-10) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 n-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 n-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 n-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 n-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 n-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 n-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 n-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 n-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 n-40) is transmitted.

The message (operation 1 n-b) including V2X SL UE capability information that the vehicle UE 1 n-01 receiving the message (e.g., V2X-SL-UECapabilityInformation) including V2X SL UE capability information transmits to the vehicle UE 1 n-02:

-   -   may be transmitted after a message (operation 1 n-a) including         V2X SL UE information is received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 n-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 n-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 n-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 n-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 n-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 n-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 n-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 n-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 n-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 n-40) is received.

When the vehicle UE 1 n-01 transmits the message (1 n-b) to the vehicle UE 1 n-02, the vehicle UE 1 n-01 can transmit the message (operation 1 n-b) to the vehicle UE 1 n-02, including only V2X SL UE capability information that the vehicle UE 1 n-01 can support, based on the message (operation 1 n-a) including the received V2X SL UE capability information. That is, the message (operation 1 n-b) may include a portion of or the entire received message (operation 1 n-a). Alternatively, the message (operation 1 n-b) may indicate only V2X SL UE capability information that can be supported in the received message (operation 1 n-a). Alternatively, the message (operation 1 n-b) may indicate only V2X SL UE capability information that cannot be supported in the received message (operation 1 n-a).

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 n-01 can perform a NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 n-02.

The vehicle UE 1 n-01 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 n-02 (operation 1 n-c). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted simultaneously with a message (operation 1         n-b) including V2X SL UE information or     -   may be multiplexed and transmitted with a message (operation 1         n-b) including V2X SL UE information or     -   may be transmitted after a message (operation 1 n-b) including         V2X SL UE information is transmitted or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 n-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 n-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 n-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 n-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 n-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 n-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 n-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 n-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 n-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 n-40) is received.

The vehicle UE 1 n-02 can receive the PC5 RRC message (operation 1 n-b) transmitted from the vehicle UE 1 n-01, and when the message is applied, the vehicle UE 1 n-02 can transmit a PC5 RRC message to inform the vehicle UE 1 j-01 that the message has been confirmed (1 n-c). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above.

-   -   The message may be transmitted after a PC5 RRC message         (operation 1 n-c) including an AS layer parameter and         configuration information that can be applied to NR V2X SL         unicast communication is received or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 n-10) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 n-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 n-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 n-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 n-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 n-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 n-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 n-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 n-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 n-40) is transmitted.

The V2X SL UE capability transfer procedure according to an embodiment of the disclosure may be referred to as a 2-operation procedure. The 2-operation may have the following advantages:

-   -   The vehicle UE 1 n-02 can transmit a message including V2X SL UE         capability information through one-time signaling to the vehicle         UE 1 n-01. That is, the signaling flow can be reduced, so         latency can be decreased.     -   When the vehicle UE 1 n-02 does not know at least some of the         V2X SL UE capability information of the vehicle UE 1 n-01, the         vehicle UE 1 n-01 performs the last operation of the         2-operation, whereby the vehicle UE 1 n-02 can know the V2X SL         UE capability information that the vehicle UE 1 n-01 supports.     -   The vehicle UE 1 n-01 performs the last operation, including         only V2X SL UE capability information that the vehicle UE 1 n-01         can support of the V2X SL UE capability information that the         vehicle UE 1 n-02 can support, to the vehicle UE 1 n-02, thereby         being able to reduce signaling overhead.

When the V2X SL UE capability transfer procedure is successfully performed, the vehicle UE 1 n-02 can perform a NR V2X SL PC5 RRC connection reconfiguration procedure to provide an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 n-01.

The vehicle UE 1 n-02 can transmit a PC5-RRC message including an AS layer parameter and configuration information that can be applied to NR V2X SL unicast communication to the vehicle UE 1 n-01 (operation 1 n-e). For example, the message may be referred to as a V2X-SL-RRCReconfiguration message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a message (operation 1 n-b) including         V2X SL UE information is received or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 n-10) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 n-20) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 n-20) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMMAND message (operation 1 n-20) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 n-20) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 n-30) is received or     -   may be transmitted before a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 n-40) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 n-40) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_ACCEPT message (operation 1 n-40) or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 n-40) is transmitted.

The vehicle UE 1 n-01 can receive the PC5 RRC message (operation 1 n-e) transmitted from the vehicle UE 1 n-02, and when the message is applied, the vehicle UE 1 n-01 can transmit a PC5 RRC message to inform the vehicle UE 1 n-02 that the message has been confirmed (1 n-f). For example, the message may be referred to as a V2X-SL-RRCReconfigurationComplete message. The message may be transmitted through an SCCH as a PC5-RRC control message. The message may include at least one of information included in the PC5-RRC message according to the embodiment described above. The message:

-   -   may be transmitted after a PC5 RRC message (operation 1 n-e)         including an AS layer parameter and configuration information         that can be applied to NR V2X SL unicast communication is         received or     -   may be transmitted before a DIRECT_COMMUNICATION_REQUEST message         (operation 1 n-10) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 n-10) or     -   may be multiplexed and transmitted with a         DIRECT_COMMUNICATION_REQUEST message (operation 1 n-10) or     -   may be transmitted after a DIRECT_COMMUNICATION_REQUEST message         (operation 1 n-10) is transmitted or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMMAND message         (operation 1 n-20) is received or     -   may be transmitted before a DIRECT_SECURITY_MODE_COMPLETE         message (operation 1 n-30) is transmitted or     -   may be transmitted simultaneously with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 n-30) or     -   may be multiplexed and transmitted with a         DIRECT_SECURITY_MODE_COMPLETE message (operation 1 n-30) or     -   may be transmitted after a DIRECT_SECURITY_MODE_COMPLETE message         (operation 1 n-30) is transmitted or     -   may be transmitted after a DIRECT_COMMUNICATION_ACCEPT message         (operation 1 n-40) is received.

The 2-operation may have the advantages described above.

When two UEs start the same procedure in accordance with an embodiment of the disclosure, the UEs can start one procedure in accordance with a received system frame number, an earlier system frame number through GNSS synchronization, or GNSS synchronization.

Procedures (FIGS. 1F to 1N) according to the disclosure may also be applied to perform NR V2X SL groupcast communication. For example, a UE corresponding to a leader and a UE corresponding to a follower or a member in a groupcast can perform a procedure according to an embodiment of the procedures (FIGS. 1F to 1N) according to the disclosure.

FIG. 1O is a diagram illustrating a structure of a user equipment according to an embodiment of the disclosure.

Referring to FIG. 1O, the UE may include a radio frequency (RF) processor 1 o-10, a baseband processor 1 o-20, a storage 1 o-30, and a controller 1 o-40.

The RF processor 1 o-10 according to an embodiment of the disclosure can perform a function for transmitting/receiving a signal through a radio channel such as changing and amplifying the band of a signal. That is, the RF processor 1 o-10 can convert upward a baseband signal provided from the baseband processor 1 o-20 into an RF band signal and then receive the RF band signal through an antenna, and can convert the RF band signal received through the antenna downward into a baseband signal. For example, the RF processor 1 o-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), etc.

Although only one antenna is shown in FIG. 1O, the UE may include several antennas.

The RF processor 1 o-10 may include several RF chains. The RF processor 1 o-10 can perform beamforming. For beamforming, the RF processor 1 o-10 can adjust the phases and intensities of signals transmitted/received through several antennas or antenna elements. The RF processor 1 o-10 can perform Multiple-Input Multiple-Output (MIMO) and can receive several layers when performing MIMO. The RF processor 1 o-10 can perform sweeping a reception beam by appropriately configuring several antennas or antenna elements or can adjust the direction and the beam width of a reception beam such that the reception beam is consonant with a transmission beam in accordance with control by the controller 1 o-40.

The baseband processor 1 o-20 can perform a conversion function among base band signals and bit strings in accordance with the physical layer specification of the system. For example, the baseband processor 1 o-20 can generate complex symbols by encoding and modulating transmission bit strings when transmitting data. Further, when receiving data, the baseband processor 1 o-20 can restore reception bit strings by demodulating or decoding a baseband signal provided from the RF processor 1 o-10. For example, according to Orthogonal Frequency Division Multiplexing (OFDM), when transmitting data, the baseband processor 1 o-20 generates complex symbols by encoding and modulating transmission bit strings, maps the complex symbols to subcarriers, and then performs Inverse Fast Fourier transform (IFFT) and Cyclic Prefix (CP), thereby being able to configure OFDM symbols. Further, when receiving data, the baseband processor 1 o-20 divides a baseband signal provided from the RF processor 1 o-10 in the unit of OFDM symbol, restores signals mapped to subcarriers through Fast Fourier Transform (FFT), and then performs demodulating or decoding, thereby being able to restore a reception bit string.

The baseband processor 1 o-20 and the RF processor 1 o-10 can transmit and receive a signal, as described above. Accordingly, the baseband processor 1 o-20 and the RF processor 1 o-10 may be referred to as a transmitter, a receiver, a transceiver, or a communicator. At least one of the baseband processor 1 o-20 and the RF processor 1 o-10 may include several communication modules to support several different radio access technologies. At least one of the baseband processor 1 o-20 and the RF processor 1 o-10 may include different communication modules to process signals of different frequency bands. For example, the different radio access technologies may include an LTE network, an NR network, etc. The different frequency bands may include Super High Frequency (SHF) bands (for example, 2.2 GHz and 2 GHz) and millimeter wave bands (for example, 60 GHz).

The storage 1 o-30 can store data such as fundamental programs, applications, and configuration information for operation of the UE. The storage 1 o-30 can provide stored data in accordance with a request from the controller 1 o-40.

The controller 1 o-40 can control general operations of the UEs. For example, the controller 1 o-40 can transmit/receive a signal through the baseband processor 1 o-20 and the RF processor 1 o-30. The controller 1 o-40 can record and read data in and from the storage 1 o-30. To this end, the controller 1 o-40 may include at least one processor 1 o-42. For example, the controller 1 o-40 may include a communication processor (CP) that controls communication and an application processor (AP) that control upper links such as applications.

FIG. 1P is a diagram illustrating a structure of a base station according to an embodiment of the disclosure.

A base station according to an embodiment of the disclosure may include one or more Transmission Reception Points (TRP).

Referring to FIG. 1P, the base station according to an embodiment of the disclosure may include an RF processor 1 p-10, a baseband processor 1 p-20, a backhaul communicator 1 p-30, a storage 1 p-40, and a controller 1 p-50.

The RF processor 1 p-10 can perform a function for transmitting/receiving a signal through a radio channel such as changing and amplifying the band of a signal. That is, the RF processor 1 p-10 can convert upward a baseband signal provided from the baseband processor 1 p-20 into an RF band signal and then receive the RF band signal through an antenna, and can convert the RF band signal received through the antenna downward into a baseband signal. For example, the RF processor 1 p-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc.

Although only one antenna is shown in FIG. 1P, the base station may include several antennas.

The RF processor 1 p-10 may include several RF chains. The RF processor 1 p-10 can perform beamforming. For beamforming, the RF processor 1 p-10 can adjust the phases and intensities of signals transmitted/received through several antennas or antenna elements. The RF processor 1 p-10 can perform downward MIMO by transmitting one or more layers.

The baseband processor 1 p-20 can perform a conversion function among base band signals and bit strings in accordance with the physical layer specification of a first radio access technology. For example, the baseband processor 1 p-20 can generate complex symbols by encoding and modulating transmission bit strings when transmitting data. Further, when receiving data, the baseband processor 1 p-20 can restore reception bit strings by demodulating or decoding a baseband signal provided from the RF processor 1 p-10. For example, according to OFDM, the baseband processor 1 p-20 generates complex symbols by encoding and modulating transmission bit strings when transmitting data, maps the complex symbols to subcarriers, and then performs IFFT and CP, thereby being able to configure OFDM symbols. Further, when receiving data, the baseband processor 1 p-20 divides a baseband signal provided from the RF processor 1 p-10 in the unit of OFDM symbol, restores signals mapped to subcarriers through FFT, and then performs demodulating or decoding, thereby being able to restore a reception bit string. The baseband processor 1 p-20 and the RF processor 1 p-10 can transmit and receive a signal, as described above.

Accordingly, the baseband processor 1 p-20 and the RF processor 1 p-10 may be referred to as a transmitter, a receiver, a transceiver, a communicator, or a radio communicator.

The communicator 1 p-30 provides an interface for communication with other nodes in the network. That is, the communicator 1 p-30 can convert a bit string transmitted from a main base station to another node, for example, a sub-base station and a core network into a physical signal and can convert a physical signal received from another node into a bit string.

The storage 1 p-40 can store data such as fundamental programs, applications, and configuration information for operation of the main base station. In particular, the storage 1 p-40 can store information about a bearer allocated to a connected UE, a measurement result reported from the connected UE, etc. The storage 1 p-40 can provide multi-connection to a UE or can store information that is the reference for determining whether to stop the multi-connection. The storage 1 p-40 can provide stored data in accordance with a request from the controller 1 p-50.

The controller 1 p-50 can control general operations of the main base station. For example, the controller 1 p-50 can transmit/receive a signal through the baseband processor 1 p-20 and the RF processor 1 p-10, or through the communicator 1 p-30. The controller 1 p-50 can record and read data in and from the storage 1 p-40. To this end, controller 1 p-50 may include at least one processor 1 p-52.

Methods according to the claims of the disclosure or the embodiments described in the specification may be implemented in hardware, software, or a combination of software and hardware.

When they are implemented in software, a computer-readable storage medium that stores one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured to be able to be executed by one or more processors in an electronic device. The one or more programs include instructions for the electronic device to perform the methods according to the claims of the disclosure or embodiments described in the specification.

Such programs (software modules, software) may be stored in a nonvolatile memory including a random access memory and a flash memory, a Read Only Memory (ROM), an Electrically Erasable Programmable Read Only Memory (EEPROM), a magnetic disc storage device, a Compact Disc-ROM (CD-ROM), Digital Versatile Discs (DVDs), or another type of optical storage device, and a magnetic cassette. Alternatively, they may be stored in a memory configured by combining some or all of the devices. Each configuration memory may be included as several pieces.

The programs may be stored in an attachable storage device that can be accessed through a communication network such as the internet, an intranet, a Local Area Network (LAN), a Wide LAN (WLAN), or a Storage Area Network (SAN), or a network configured by combining them. The storage device can access a device that performs embodiments of the disclosure through an external port. A separate storage device in a communication network can access a device that performs the embodiments of the disclosure.

In the detailed embodiment of the disclosure described above, the components included in the disclosure were described in singular forms or plural forms, depending on the proposed detailed embodiments. However, the singular or plural expressions were appropriately selected in the proposed situations for the convenience of description and the disclosure is not limited to the singular or plural components. Further, even if components are described in a plural form, they may be singular components, or even if components are described in a singular form, they may be plural components.

Although detailed embodiments were described above, various modifications are possible without departing from the scope of the disclosure. Accordingly, the range of the disclosure is not limited to the embodiments and should be defined by not only the range of the claims described below, but also equivalents to the range of the claims.

Second Embodiment

In the following description of the disclosure, detailed descriptions of well-known functions or configurations relating to the disclosure will not be provided so as not to obscure the description of the disclosure with unnecessary details. Hereinafter, embodiments of the disclosure are described with reference to the accompanying drawings.

FIG. 2A is a diagram illustrating a structure of a next generation mobile communication system according to an embodiment of the disclosure.

Referring to FIG. 2A, as shown in the figure, a radio access network of a next generation mobile communication system (new radio, NR) may be composed of a new radio node B (hereafter, a gNB) 2 a-10 and an access and mobility management function (AMF) (New Radio Core Network) 2 a-05. A new radio user equipment (hereafter, a NR UE or UE) 2 a-15 in a cell 2 a-20 is connected to an external network through the gNB 2 a-10 and the AMF 2 a-05.

In FIG. 2A, the gNB correspond to an Evolved Node B (eNB) of an existing LTE system. The gNB is connected with the NR UE through a radio channel and can provide an excellent service more than an existing node B. In the next generation mobile communication system, all user traffics are served through a shared channel, so there is a need for a device that performs scheduling by combining state information such as a buffer state, an available power state, and a channel state of UEs, and the gNB 2 g-10 takes charge of the device. One gNB generally controls several cells. In order to implement high-speed data transmission faster than existing LTE, a bandwidth over an existing maximum bandwidth may be provided, and a beamforming technology may be additionally employed by using orthogonal frequency division multiplexing (hereafter, referred to as OFDM) as a radio access technology. It is also possible to apply modulation scheme and Adaptive Modulation & Coding (hereafter, referred to as AMC) determining a channel coding rate, depending on the channel state of a user equipment. The AMF 2 a-05 performs functions such as supporting mobility, configuring a bearer, and configuring QoS. The AMF, which is a device being in charge of not only a mobility management function for UEs, but also various control functions, is connected to several base stations. The next generation mobile communication system can operate with an existing LTE system and the AMF is connected with an MME 2 a-25 through a network interface. The MME is connected with an eNB 2 a-30 that is an existing base station. A UE supporting LTE-NR Dual Connectivity can transmit/receive data while maintaining connection with not only the gNB, but also the eNB (2 a-35).

FIG. 2B is a diagram illustrating a dual-connectivity scenario in a next generation mobile communication system according to an embodiment of the disclosure.

Referring to FIG. 2B, Dual Connectivity (DC) refers to a technology that is connected with a plurality of base stations 2 b-05 and 2 b-10 and is provided with a radio communication service. The first base station 2 b-05, which is a Master Node (MN), configures one or more serving cells of the second base station 2 b-10, that is, a Secondary Node (SN) to a UE 2 b-20. If both of the first base station and the second base station are NR base stations, they are referred as NR-DCs, if the first base station is an LTE base station and the second base station of an NR base station, they are referred to as EN-DCs, and if the first base station is an NR base station and the second base station is an LTE base station, they are referred to as NE-DCs. The serving cells of each base station can serve the UE 2 b-20 using different frequencies. In general, a low frequency range (450-6000 MHz) is referred to as an FR1 and a high frequency range (24250-52600 MHz) is referred to as an FR2. For example, the first cell 2 b-25 that the first base station provides pertains to the FR1 and the second cell 2 b-30 pertains to the FR2, and the third cell 2 b-35 that the second base station provides pertains to the FR2.

In the disclosure, it may be possible to consider a situation in which macro cells and micro cells exist together. The macro cell, which is a cell that is controlled by a macro base station, provides a service in a relative wide area. In this case, the macro cell may be composed of an LTE base station MeNB and an LTE base station SeNB. As another embodiment, in this case, the macro cell may be composed of an LTE (MeNB) base station and an NR base station SgNB. As another embodiment, in this case, the macro cell may be composed of an NR (MgNB) base station and an LTE base station SgNB. As another embodiment, in this case, the macro cell may be composed of an NR (MgNB) base station and an NR base station SgNB.

A base station can configure a measurement gap 2 b-15 that temporarily stops data transmission/reception to a UE to measure another frequency.

In a DC scenario, the MN can configure a measurement gap that is applied to the serving cells of the MN or the SN and the SN can also configure a measurement gap that is applied to the serving cells of the SN. The measurement gap is largely classified into three kinds. A per-UE gap is applied to all serving cells configured in a UE. An FR1 gap is applied to serving cells pertaining to the FR1. An FR2 gap is applied to serving cells pertaining to the FR2. As for the EN-DC, the MN can configure all of the per-UE gap, FR1 gap, and FR2 gap and the SN can configure only the FR2 gap. When the per-UE gap is configured, the RF1 gap and the FR2 gap can be configured. The configuration information of the gaps includes the following information:

-   -   gapOffset: offset information of gap pattern     -   mgl: length of gap     -   mgrp: repetitive cycle of gap     -   mgta: gap timing advance information

A UE receiving the information can derive a radio frame and a subframe at which the gaps start through the following formula: SFN mod T=FLOOR(gapOffset/10) subframe=gapOffset mod 10 where T=MGRP/10  Formula 1

An SFN and a subframe timing that are references are required to derive an actual gap period from the formula. In a DC, a plurality of serving cells may exist and the SFN and the subframe timing of the serving cells may be different. Accordingly, it is required to use the SFN and the subframe of which serving cell as references.

The disclosure proposes a method of selecting a serving cell that is the reference from various DC scenarios such as the EN-DC, NR-DC, and NE-DC.

A 2-1 embodiment is characterized by driving a gap, based on the SFN and the subframe of a special cell of a base station configuring the gas configuration information. A base station that configured one item of gap configuration information and a base station providing the information to a UE may be different. For example:

-   -   In case 1: If gap configuration information is provided through         an RRCReconfiguration message pertaining to an SBR1, the         configuration information is configured and provided to a UE by         an MN.     -   In case 2: If gap configuration information is provided through         an RRCReconfiguration message pertaining to an SBR3, the         configuration information is configured and provided to a UE by         an SN. The corresponding DC scenario is an NR-DC or an EN-DC.     -   In case 3: If gap configuration information is accommodated in         an nr-SCG (a container accommodating NR SCG-related         configuration information) and provided from an         RRCReconfiguration message pertaining to the SRB1, the         configuration information is configured by an SN and is provided         to a UE by an MN. The corresponding DC scenario is an NR-DC.     -   In case 4: If gap configuration information is accommodated in         an eutra-SCG (a container accommodating EUTRA SCG-related         configuration information) and provided from an         RRCReconfiguration message pertaining to the SRB1, the         configuration information is configured by an SN and is provided         to a UE by an MN. The corresponding DC scenario is an NE-DC.     -   In case 5: If gap configuration information is accommodated in         an NR container and provided from an         RRCConnectionReconfiguration message pertaining to the SRB1, the         configuration information is configured by an SN and is provided         to a UE by an MN. The corresponding DC scenario is an EN-DC.

In consideration of a node in which the gap configuration information is configured, the case 1 selects PCell, the case 2 selects PSCell, the case 3 selects PSCell, the case 4 selects PSCell, and the case 5 selects PSCell as reference cells, respectively, and the SFN and the subframe numbers of the serving cells are applied to the formula.

A 2-2 embodiment is characterized by applying the SFN and the timing of the subframe of PSCell only to the FR2 gap in the EN-DC. The SFN and the timing of the subframe of PCell are applied to all of the other DC scenario, NR-DC, and NE-DC except for the EN-DC. A UE receiving an RRCReconfiguration message including measConfig determines a reference serving cell. The method of selecting the reference serving cell in the 2-2 embodiment is as follows.

If it is a per-UE gap/FR1 gap, a gap timing is calculated by applying the SFN and the subframe number of the PCell.

If it is FR2 gap and the EN-DC is configured, that is, if the PCell is an LTE cell and an MCG is composed of LTE serving cells or the MCG is LTE, the gap timing is calculated by applying the SFN and the subframe number of the PSCell pertaining to the FR2.

When it is the FR2gap and the EN-DC is not configured, that is, an NR SA, an NE-DC, and an NR-DC are configured, or the MCG is an NR, the gap timing is calculated by applying the SFN and the subframe number of the PCell.

If it is the per-UE gap during the determined gap time period, downlink reception and uplink transmission are stopped in all serving cells, if it is the FR1 gap, downlink reception and uplink transmission are stopped in all serving cells pertaining to the FR1, and if it is the FR2 gap, downlink reception and uplink transmission are stopped in all serving cells pertaining to the FR2.

FIGS. 2CA and 2CB are flowcharts illustrating a user equipment process of applying cell measurement period configuration in a dual connectivity scenario in the 2-1 embodiment according to various embodiments of the disclosure.

Referring to FIGS. 2CA and 2CB, a UE is connected with an MN in operation 2 c-05.

In operation 2 c-10, the UE receives configuration information related to SN connection from the MN and performs dual connectivity.

In operation 2 c-15, the UE receives measurement configuration information including gap configuration information from the MN or the SN.

In operation 2 c-20, the UE determines the DC scenario that is being applied.

In operation 2 c-25, if it is an EN-DC, the UE determines what kind of gap has been configured.

In operation 2 c-30, if it is a per-UE or an FR1 gap, the SFN and the subframe of PCell are applied to the gap calculation.

In operation 2 c-35, if it is an FR2 gap, the SFN and the subframe of PSCell are applied to the gap calculation.

In operation 2 c-40, the per-UE gap is applied to all serving cells configured in the UE. The FR1 gap is applied to serving cells pertaining to the FR1. The FR2 gap is applied to serving cells pertaining to the FR2. The UE stops downlink reception and uplink transmission during the gap time period.

In operation 2 c-45, if it is an NR-DC or an NE-DC and the gap configuration information has been received through an RRCReconfiguration message pertaining to the SRB1, the SFN and the subframe of the PCell are applied to the gap calculation.

In operation 2 c-50, if it is an NR-DC or an NE-DC and the gap configuration information has not been received through an RRCReconfiguration message pertaining to the SRB1, the SFN and the subframe of the PSCell are applied to the cap calculation.

In operation 2 c-55, the per-UE gap is applied to all serving cells configured in the UE. The FR1 gap is applied to serving cells pertaining to the FR1. The FR2 gap is applied to serving cells pertaining to the FR2. The UE stops downlink reception and uplink transmission during the gap time period.

FIG. 2D is a flowchart illustrating a user equipment process of applying cell measurement period configuration in a dual-connection scenario in a 2-2 embodiment according to an embodiment of the disclosure.

Referring to FIG. 2D, a UE is connected with an MN in operation 2 d-05.

In operation 2 d-10, the UE receives configuration information related to SN connection from the MN and performs dual connectivity.

In operation 2 d-15, the UE receives measurement configuration information including gap configuration information from the MN or the SN.

In operation 2 d-20, the UE determines whether the EN-DC has been configured and FR2 gap configuration information has been provided.

In operation 2 d-25, if the EN-DC has been configured and the FR2 gap configuration information has been provided, the SFN and the subframe of the PSCell are applied to the gap calculation.

In operation 2 d-30, the per-UE gap is applied to all serving cells configured in the UE. The FR1 gap is applied to serving cells pertaining to the FR1. The FR2 gap is applied to serving cells pertaining to the FR2. The UE stops downlink reception and uplink transmission during the gap time period.

In operation 2 d-35, if per-UE gap or FR1 gap configuration information has been provided or if the EN-DC has not been configured and the FR2 gap configuration information has been provided, the SFN and the subframe of the PCell are applied to the gap calculation.

In operation 2 d-40, the per-UE gap is applied to all serving cells configured in the UE. The FR1 gap is applied to serving cells pertaining to the FR1. The FR2 gap is applied to serving cells pertaining to the FR2. The UE stops downlink reception and uplink transmission during the gap time period.

FIG. 2E illustrates the structure of a UE according to an embodiment of the disclosure.

Referring to FIG. 2E, the UE includes a Radio Frequency (RF) processor 2 e-10, a baseband processor 2 e-20, a storage 2 e-30, and a controller 2 e-40.

The RF processor 2 e-10 performs a function for transmitting/receiving a signal through a radio channel such as changing and amplifying the band of a signal. That is, the RF processor 2 e-10 converts upward a baseband signal provided from the baseband processor 2 e-20 into an RF band signal and then receives the RF band signal through an antenna, and converts the RF band signal received through the antenna downward into a baseband signal. For example, the RF processor 2 e-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), etc. Although only one antenna is shown in the figure, the UE may have several antennas. The RF processor 2 e-10 may include several RF chains. The RF processor 2 e-10 can perform beamforming. For beamforming, the RF processor 2 e-10 can adjust the phases and intensities of signals transmitted/received through several antennas or antenna elements. The RF processor can perform MIMO and can receive several layers when performing MIMO.

The baseband processor 2 e-20 performs a conversion function among base band signals and bit strings in accordance with the physical layer specification of the system. For example, the baseband processor 2 e-20 generates complex symbols by encoding and modulating transmission bit strings when transmitting data. When receiving data, the baseband processor 2 e-20 restores a reception bit string by demodulating and decoding a baseband signal provided from the RF processor 2 e-10. For example, according to Orthogonal Frequency Division Multiplexing (OFDM), the baseband processor 2 e-20 generates complex symbols by encoding and modulating transmission bit strings when transmitting data, maps the complex symbols to subcarriers, and then performs Inverse Fast Fourier transform (IFFT) and Cyclic Prefix (CP), thereby configuring OFDM symbols. Further, when receiving data, the baseband processor 2 e-20 divides a baseband signal provided from the RF processor 2 e-10 in the unit of OFDM symbol, restores signals mapped to subcarriers through Fast Fourier Transform (FFT), and then performs demodulating or decoding, thereby restoring a reception bit string.

The baseband processor 2 e-20 and the RF processor 2 e-10 transmit and receive a signal, as described above. Accordingly, the baseband processor 2 e-20 and the RF processor 2 e-10 may be referred to as a transmitter, a receiver, a transceiver, or a communicator. At least one of the baseband processor 2 e-20 and the RF processor 2 e-10 may include several communication modules to support several different radio access technologies. At least one of the baseband processor 2 e-20 and the RF processor 2 e-10 may include different communication modules to process signals of different frequency bands. For example, the different radio access technologies may include a radio LAN (e.g., IEEE 802.11) and a cellular network (e.g., LTE). The different frequency bands may include Super High Frequency (SHF) bands (for example, 2.NRHz and NRhz) and millimeter wave bands (for example, 60 GHz).

The storage 2 e-30 keeps data such as fundamental programs, applications, and setting information for operation of the UE. In particular, the storage 2 e-30 can store information about a second access node that performs radio communication using a second radio access technology. The storage 2 e-30 provides stored data in accordance with a request from the controller 2 e-40.

The controller 2 e-40 controls general operations of the UE. For example, the controller 2 e-40 transmits and receives a signal through the baseband processor 2 e-20 and the RF processor 2 e-10. The controller 2 e-40 records and reads data in and from the storage 2 e-30. To this end, the controller 1 o-40 may include at least one processor. For example, the controller 2 e-40 may include a communication processor (CP) 2 e-42 that controls communication and an application processor (AP) that control upper links such as applications.

FIG. 2F illustrates a block configuration of a main base station in a radio communication system according to an embodiment of the disclosure.

Referring to FIG. 2F, the base station includes an RF processor 2 f-10, a baseband processor 2 f-20, a backhaul communicator 2 f-30, a storage 2 f-40, and a controller 2 f-50.

The RF processor 2 f-10 performs a function for transmitting/receiving a signal through a radio channel such as changing and amplifying the band of a signal. That is, the RF processor 2 f-10 converts upward a baseband signal provided from the baseband processor 2 f-20 into an RF band signal and then transmits the RF band signal through an antenna, and converts the RF band signal received through the antenna downward into a baseband signal. For example, the RF processor 2 f-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. Although only one antenna is shown in the figure, the first access node may have several antennas. The RF processor 2 f-10 may include several RF chains. The RF processor 2 f-10 can perform beamforming. For beamforming, the RF processor 2 f-10 can adjust the phases and intensities of signals transmitted/received through several antennas or antenna elements. The RF processor can perform downward MIMO by transmitting one or more layers.

The baseband processor 2 f-20 performs a conversion function among base band signals and bit strings in accordance with the physical layer specification of a first radio access technology. For example, the baseband processor 2 f-20 generates complex symbols by encoding and modulating transmission bit strings when transmitting data. When receiving data, the baseband processor 2 f-20 restores a reception bit string by demodulating and decoding a baseband signal provided from the RF processor 2 f-10. For example, according to OFDM, the baseband processor 2 f-20 generates complex symbols by encoding and modulating transmission bit strings when transmitting data, maps the complex symbols to subcarriers, and then performs IFFT and CP, thereby configuring OFDM symbols. Further, when receiving data, the baseband processor 2 f-20 divides a baseband signal provided from the RF processor 2 f-10 in the unit of OFDM symbol, restores signals mapped to subcarriers through FFT, and then performs demodulating or decoding, thereby restoring a reception bit string. The baseband processor 2 f-20 and the RF processor 2 f-10 transmit and receive a signal, as described above. Accordingly, the baseband processor 2 f-20 and the RF processor 2 f-10 may be referred to as a transmitter, a receiver, a transceiver, a communicator, or a radio communicator.

The backhaul communicator 2 f-30 provides an interface for communication with other nodes in the network. That is, the backhaul communicator 2 f-30 converts a bit string transmitted from a main base station to another node, for example, a sub-base station and a core network into a physical signal and converts a physical signal received from another node into a bit string.

The storage 2 f-40 keeps data such as fundamental programs, applications, and setting information for operation of the main base station. In particular, the storage 2 f-40 can store information about a bearer allocated to a connected UE, a measurement result reported from the connected UE, etc. The storage 2 f-40 can provide multi-connection to a UE or can store information that is the reference for determining whether to stop the multi-connection. The storage 2 f-40 provides stored data in accordance with a request from the controller 2 f-50.

The controller 2 f-50 controls general operations of the main base station. For example, the controller 2 f-50 transmits and receives a signal through the baseband processor 2 e-20 and the RF processor 2 e-10, or through the backhaul communicator 2 f-30. The controller 2 f-50 records and reads data in and from the storage 2 f-40. To this end, controller 2 f-50 may include at least one processor. 2 f-52

While the disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. 

What is claimed is:
 1. A method performed by a first user equipment (UE) in a radio communication system, the method comprising: transmitting, to a second UE, a UECapabilityEnquirySidelink message for requesting a sidelink UE capability of the second UE, wherein the UECapabilityEnquirySidelink message includes information associated with a sidelink UE capability including a radio access capability of the first UE and information to request a filtered sidelink UE capability of the second UE; receiving, from the second UE, a message including information associated with the filtered sidelink UE capability of the second UE, in response to transmission of the UECapabilityEnquirySidelink message; and transmitting a radio resource control (RRC) message including at least one of information related to a sidelink signaling radio bearer (SRB), information related to a sidelink data radio bearer (DRB), or resource pool, based on the received information associated with the filtered sidelink UE capability of the second UE.
 2. The method of claim 1, wherein the radio access capability includes radio access technology (RAT) information.
 3. The method of claim 1, further comprising performing a discovery procedure for sidelink unicast communication between the first UE and the second UE.
 4. A method performed by a second user equipment (UE) in a radio communication system, the method comprising: receiving, from a first UE, a UECapabilityEnquirySidelink message requesting for a sidelink UE capability of the second UE, wherein the UECapabilityEnquirySidelink message includes information associated with a sidelink UE capability including a radio access capability of the first UE and information to request a filtered sidelink UE capability of the second UE; transmitting, to the first UE, a message including information associated with the filtered sidelink UE capability of the second UE, in response to reception of the UECapabilityEnquirySidelink message; and receiving a radio resource control (RRC) message including at least one of information related to a sidelink signaling radio bearer (SRB), information related to a sidelink data radio bearer (DRB), or resource pool, based on the transmitted information associated with the filtered sidelink UE capability of the second UE.
 5. The method of claim 4, wherein the radio access capability includes radio access technology (RAT) information.
 6. The method of claim 4, further comprising performing a discovery procedure for sidelink unicast communication by between the first UE and the second UE.
 7. A first user equipment (UE) comprising: a transceiver; and at least one processor configured to: control the transceiver to transmit, to a second UE, a UECapabilityEnquirySidelink message requesting fora sidelink UE capability of the second UE, wherein the UECapabilityEnquirySidelink message includes information associated with a sidelink UE capability including a radio access capability of the first UE and information to request a filtered sidelink UE capability of the second UE, control the transceiver to receive, from the second UE, a message including information associated with the filtered sidelink UE capability of the second UE, in response to transmission of the UECapabilityEnquirySidelink message, and control the transceiver to transmit a radio resource control (RRC) message including at least one of information related to a sidelink signaling radio bearer (SRB), information related to a sidelink data radio bearer (DRB), or resource pool, based on the received information associated with the filtered sidelink UE capability of the second UE.
 8. The first user equipment of claim 7, wherein the radio access capability includes radio access technology (RAT) information.
 9. The first UE of claim 7, wherein the at least one processor is further configured to perform a discovery procedure for sidelink unicast communication between the first UE and the second UE.
 10. A second user equipment (UE) comprising: a transceiver; and at least one processor configured to: control the transceiver to receive, from a first UE, a UECapabilityEnquirySidelink message requesting fora sidelink UE capability of the second UE, wherein the UECapabilityEnquirySidelink message includes information associated with a sidelink UE capability including a radio access capability of the first UE and information to request a filtered sidelink UE capability of the second UE, control the transceiver to transmit, to the first UE, a message including information associated with the filtered sidelink UE capability of the second UE, in response to reception of the UECapabilityEnquirySidelink message, and control the transceiver to receive a radio resource control (RRC) message including at least one of information related to a sidelink signaling radio bearer (SRB), information related to a sidelink data radio bearer (DRB), or resource pool, based on the transmitted information associated with the filtered sidelink UE capability of the second UE.
 11. The second user equipment of claim 10, wherein the radio access capability includes radio access technology (RAT) information.
 12. The second UE of claim 10, wherein the at least one processor is further configured such that the first UE and the second UE perform a discovery procedure for sidelink unicast communication. 